Texas lnstruments bq2040 handbook
Contents
1. ucc Qt DS TPS t Ivf KI BAT BAUSS TPG R11 vec C2 R16 D8 _ cMPz4691 U Si R5 U2 R13 R12 j Optional iz 1 8 10K 10K 1 2 Ai i Z 1 Vcc Ui Your 16 t 3 A2 SCL 2 r 2 ESCL REF a TP4 gt i T Hea aen 2ALCOI 5 tebe pstat 2 Sie ear Ostat N Z LED4 disp 18 a a Bo Ves sr 2 E bq2040 R17 Cl R4 ucc ucc z gt R3 D1 CS 10K 1UF 1 Y te N I r _ COLOR 1UF R8 Rg R14 D2 SMBC D 100 108 O Is COLOR SW1 l D7 R2 D3 o o Y DISPLAY 1k coLoa BZxB4CSUS R15 D4 Ny RG DE 4 Ik COLOR ad K pa BZxe4CSUS Chart 1 SMBD For bq2040 With No D8 No of Cells R5 R11 R4 Qi O PACK 2 301k 604K 100K Bss138 Q 3 499K 806K 100K BSS138 4 698k 604K 100K 2N7002 lt TPS R1 R18 0 05 Optional 6 499k 499K 100K BSS138 R1 3H 8 698K 806K 100K BSS138 O BAT I 100K 9 Boek 499K 100K 2N7002 Z 10 909K 604K 100K 2N7002 LK 63 12 909K 909K 86 5K 2N7002 al eae 2040LED eps Figure 1 Battery Pack Application Diagram LED Display bq2040 Table 1 Configuration Memory Map AT step step for AT At termination Parameter Name Address Description Length Units EEPROM length ee Shits2. bq2040 1 7 1 1 8 g Battery Address 0001011 Write Word 1 8 1 1 7 1 Battery Address s 6001011 8 1 8 1 Pre V Data byte low A Data byte hight A P Read Word 1 7 8 1 1 8 1 8 Block Read 8 1 1 1 1 poren p ooreo porey VA Command Code Aa Data byte low VAJ Data byte high fA P 1 7 1 pome AJ sto as E vA Command Code d S Battery Address 1 4 oe 14 is ea Ls Pato 0 PA commana Code fA s Battery Adcress 1 VA n 1 8 8 1 1 6 te Count Ay aly Data byte 1 Jay Data byte 27 A Y Data byte NAA P 8 System Host bq2040 A ACKNOWLEDGE A NOT ACKNOWLEDGE S START P STOP FG204001 eps Figure 3 Host Communication Protocols m Read block The particular protocol used is a function of the com mand The protocols used are shown in Figure 3 Host to bq2040 Messages see Table 4 ManufacturerAccess 0x00 This read write word is an open location Input Output word RemainingCapacityAlarm 0x01 This function sets or returns the low capacity alarm value When RM falls below the RemainingCapac ityAlarm value initialized from the external EE PROM the Remaining Capacity_Alarm bit is set in BatteryStatus The system may alter this alarm dur ing operation Input Output unsigned integer This sets returns the value where the Remaining Capacity_Alarm bit is set in Battery Status Units mAh Range 0 to 65 535mAh Remaining Time
3. Alarm Bits Bit Name OVER_CHARGED_ALARM Set When The bq2040 detects a AT At or cur rent taper termination Note AT At and current taper are valid charge terminations Reset When A discharge occurs or when the AT At or current taper termination condition ceases during charge TERMINATE_CHARGE_ALARM The bq2040 detects an over current over voltage over temperature AT At or current taper condition during charge A discharge occurs or when all condi tions causing the event cease OVER_TEMP_ALARM The bq2040 detects that its internal temperature is greater than the pro grammed value Internal temperature falls to 43 C or the maximum temperature threshold minus 5 C TERMINATE_DISCHARGE_ALARM The bq2040 determines that it has supplied all the charge that it can without being damaged Voltage lt EDVF Voltage gt EDVF signifies that the battery has reached a state of charge sufficient for it to once again safely supply power REMAINING_CAPACITY_ALARM The bq2040 detects that the Remain ingCapacity is less than that set by the RemainingCapacityAlarm func tion Either the value set by the Remain ingCapacityAlarm function is lower than the Remaining Capacity or the RemainingCapacity is increased by charging REMAINING_TIME_ALARM The bq2040 detects that the esti mated remaining time at the present discharge rate is less than that set by the RemainingTimeAlarm f
4. 2005 Texas Instruments Incorporated
5. 0x04 This read write word is the first half of a two function set used to set the AtRate value used in calculations made by the AtRateTimeToFull and AtRateTime ToEmpty bq2040 Table 4 bq2040 Register Functions Function Code Access Units Defaults ManufacturerAccess 0x00 read write RemaningCapacityAlarm 0x01 read write mAh E RemainingTimeAlarm 0x02 read write minutes E BatteryMode 0x03 read write bit flag AtRate 0x04 read write mA AtRateTimeToFull 0x05 read minutes AtRateTimeToEmpty 0x06 read minutes AtRateOK 0x07 read Boolean Temperature 0x08 read 0 1 K 2930 Voltage 0x09 read mV E Current 0x0a read mA 0 AverageCurrent 0x0b read mA 0 MaxError 0Ox0c read percent 100 RelativeStateOfCharge 0x0d read percent AbsoluteStateOfCharge 0x0e read percent RemainingCapacity Ox0f read mAh E FullChargeCapacity 0x10 read mAh E RunTimeToEmpty 0x11 read minutes AverageTimeToEmpty 0x12 read minutes AverageTimeToFull 0x13 read minutes ChargingCurrent 0x14 read mA E ChargingVoltage 0x15 read mV E Battery Status 0x16 read bit flags E CycleCount 0x17 read cycle E DesignCapacity 0x18 read mAh E DesignVoltage 0x19 read mV E SpecificationInfo Oxla read E ManufactureDate Ox1b read E SerialNumber Oxic read integer E Reserved Oxld Ox1f ManufacturerName 0x20 read string E DeviceName 0x21 read
6. Level 1 220C UNLIM BQ2040SN D111TR ACTIVE SOIC D 16 2500 None CU NIPDAU Level 1 220C UNLIM BQ2040SN D111TRG4 PREVIEW SOIC D 16 2500 None Call TI Call TI The marketing status values are defined as follows ACTIVE Product device recommended for new designs LIFEBUY TI has announced that the device will be discontinued and a lifetime buy period is in effect NRND Not recommended for new designs Device is in production to support existing customers but TI does not recommend using this part in a new design PREVIEW Device has been announced but is not in production Samples may or may not be available OBSOLETE TI has discontinued the production of the device 2 Eco Plan May not be currently available please check http www ti com productcontent for the latest availability information and additional product content details None Not yet available Lead Pb Free Pb Free RoHS TI s terms Lead Free or Pb Free mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances including the requirement that lead not exceed 0 1 by weight in homogeneous materials Where designed to be soldered at high temperatures TI Pb Free products are suitable for use in specified lead free processes Green RoHS amp no Sb Br TI defines Green to mean Pb Free and in addition uses package materials that do not contain halogens including bromine Br or antimony Sb above 0 1 of total product wei
7. after calibration AverageCurrent 0x0b This read only word returns a rolling average of the cur rent through the battery s terminals The AverageCur rent function returns meaningful values after the bat tery s first minute of operation Output signed integer Returns the charge dis charge rate in mA where positive is for charge and negative is for discharge Units mA Range 0 to 32 767mA for charge or 0 to 32 768mA for discharge Granularity 0 2 of the DesignCapacity or better Accuracy 1 of the DesignCapacity after cali bration MaxError Ox0c Returns the expected margin of error in the state of charge calculation Output unsigned integer Returns the percent un certainty for selected information Units Range 0 to 100 RelativeStateOfCharge 0x0d This read only word returns the predicted remaining battery capacity expressed as a percentage of FullChar geCapacity RelativeStateOfCharge is only valid for battery capacities more than 1504mAh and less than 10 400mAh Output unsigned integer Returns the percent of re maining capacity Units Range 0 to 100 Granularity 1 Accuracy MaxError after circuit and capacity calibration AbsoluteStateOfCharge 0x0e This read only word returns the predicted remaining battery capacity expressed as a percentage of DesignCa pacity Note that AbsoluteStateOfCharge can return values greater than 100 Absolute StateOfC
8. and stops counting at EDV1 on discharge The DCR does not roll over but stops counting when it reaches FFFFh FCC is updated on the first charge after a qualified discharge to EDV1 The updated FCC equals the battery low percentage times the current FCC plus the DCR value A qualified discharge to EDV1 oc curs if all of the following conditions exist a No valid charge initiations charges greater than 10mAh where Vsro gt Vsrp occurred during the period between RM FCC and EDV1 de tected m The self discharge count is not more than 256mAh m The low temperature fault bit in FLAGS2 is not set when the EDV1 level is reached during dis charge a Battery voltage is not more than 256mV below the EDV1 threshold when EDV1 is set The valid discharge flag VDQ in FLAGS1 indi cates whether the present discharge is valid for an FCC update FCC cannot be reduced by more than 256mAh during any single cycle bq2040 Charge Counting Charge activity is detected based on a positive voltage on the SR input If charge activity is detected the bq2040 increments RM at a rate proportional to Vsro and if enabled activates an LED display Charge ac tions increment the RM after compensation for charge state and temperature The bq2040 determines charge activity sustained at a continuous rate equivalent to Vsro gt Vsrp A valid charge equates to sustained charge activity greater than 10 mAh Once a valid charge is detected ch
9. detected The Valid Charge flag VQ bit 5 is set when Vsro gt Vsrp and 10mAh of charge has accumulated This bit is cleared during a discharge and when Vsro lt Vsrp FLAGS1 Bits 7 6 5 4 3 2 1 0 7 VQ a x p z The VQ value is Where VQ is 0 Vsro lt Vsrp 1 Vsro 2 Vsrp and 10mAh of charge has accumulated Bit 4 is reserved The Valid Discharge flag VDQ bit 3 is set when a valid discharge is occurring discharge cycle valid for learning new full charge capacity and cleared if a par tial charge is detected EDV1 is asserted when T lt 0 C or self discharge accounts for more than 256mAh of the discharge FLAGS 1 Bits 7 6 5 4 3 2 1 0 z 7 z VDQ R The VDQ value is Where VDQ is 0 Self discharge is greater than 256mAh EDV1 1 when T lt 0 C or VQ 1 1 On first discharge after RM FCC The Overload flag OVLD bit 2 is set when the dis charge current is greater than the programmed rate and cleared when the discharge current falls below the pro grammed rate FLAGS 1 Bits FLAGS 1 Bits 4 3 Imn 4 3 2 OVLD 19 bq2040 The OVLD value is Where OVLD is 0 1 Current gt programmed rate The First End of Discharge Voltage flag EDV1 bit 1 is set when Voltage lt EDV1 and OVLD 0 and cleared when VQ 1 and
10. discharge rate per day at room temperature Voltage gain is packed as two units For example R4 at R5 R4 7 09 would be stored as whole number Voltage gain 0x56 0x57 17 07 1 99 stored in 0x57 as 7 and the decimal component stored in 0x56 as 256 x 0 09 23 17h Reserved 0x58 0x59 00 00 0 Should be programmed to 0 ns harging Ox5a Ox5b 64 00 100mA Contains the desired charge current below EDVF End of discharge OxBe OxBd 20 d1 12000mV The value programmed is the two s complement of the voltage 1 threshold voltage in mV End of discharge Oxbe Ox5f 40 aa 11200mV The value programmed is the two s complement of the voltage final threshold voltage in mV eae 0x60 0x61 d0 07 2000mA This value sets the initial estimated pack capacity The At step for AT At termination equals At step 0x62 of 20s 320 byte value 20 Hold off time 0x63 00 320s hold off The hold off time is 320 byte value 20 EEPROM check 2 0x64 b5 181 Must be equal to Oxb5 Reserved 0x65 Ox7f NA Not currently used by the bq2040 Note 1 Can be adjusted to calibrate the battery pack 25 bq2040 Table 11 Example Register Contents String Data Ox Ox Ox Ox 0x 0x 0x 0x 0x 0x 0x 0x String Description Address X0 X1 X2 X3 X4 X5 X6 X7 X8 x9 Xa Xb Man facturer name 0x20 09 42 45 4e 43 48 4d 41 52 51 7 y 0x2b B E N C H M A R Q Devi 0x30 06 42 51 32 30 34 30 evice name 0x37 B Q 2 0 4 0
11. figuration memory Functional Description General Operation The bq2040 determines battery capacity by monitoring the amount of charge put into or removed from a re chargeable battery The bq2040 measures discharge and charge currents estimates self discharge and monitors the battery for low battery voltage thresholds The charge is measured by monitoring the voltage across a small value series sense resistor between the battery s negative terminal and ground The available battery charge is determined by monitoring this voltage over time and correcting the measurement for the envi ronmental and operating conditions bq2040 Figure 1 shows a typical battery pack application of the bq2040 using the LED capacity display the serial port and an external EEPROM for battery pack program ming information The bq2040 must be configured and calibrated for the battery specific information to ensure proper operation Table 1 outlines the configuration in formation that must be programmed in the EEPROM An internal temperature sensor eliminates the need for an external thermistor reducing cost and compo nents An internal temperature compensated time base eliminates the need for an external resonator further reducing cost and components The entire cir cuit in Figure 1 can occupy less than square inch of board space
12. i 0x40 6c 69 4f 4e Device chemistry 0x45 04 L I O N 0x50 42 51 32 30 32 Manufacturer data 0x55 05 B Q 2 0 9 26 bq2040 Absolute Maximum Ratings Symbol Parameter Minimum Maximum Unit Notes Vece Relative to Vss 0 3 7 0 V All other pins Relative to Vss 0 3 7 0 V REF Relative to Vss 0 3 8 5 V Current limited by R11 see Figure 1 Minimum 1009 series resistor should VSR Relative to Vss 0 3 7 0 V be used to protect SR in case of a shorted battery TOPR Operating tempera 0 70 C Commercial ture Note Permanent device damage may occur if Absolute Maximum Ratings are exceeded Functional opera tion should be limited to the Recommended DC Operating Conditions detailed in this data sheet Expo sure to conditions beyond the operational limits for extended periods of time may affect device reliability DC Voltage Thresholds ta TOPR V 3 0 to 5 5V Symbol Parameter Minimum Typical Maximum Unit Notes Evss Battery voltage error relative to SB 50mV 50mV V See note Note The accuracy of the voltage measurement may be improved by adjusting the battery voltage offset and gain stored in external EEPROM For best operation Vcc should be 1 5V greater than Vsp 27 bq2040 Recommended DC Operating Conditions ta Topr S
13. immediately after an AtRate command Output unsigned integer Returns the predicted time to empty Units minutes Range 0 to 65 534min Granularity 2min or better Invalid Data Indication 65 535 indicates that the AtRate value is not negative AiRateOK 0x07 This read only word returns a Boolean value that indi cates whether or not the EDVF flag has been set Boolean Indicates if the battery can supply addi tional energy Units Boolean Range TRUE 0 FALSE 0 14 Temperature 0x08 This read only word returns the cell pack s internal temperature Output unsigned integer Returns the cell tem perature in tenths of degrees Kelvin increments Units 0 1 K Range 0 to 500 0 K Granularity 0 5 K or better Accuracy 3 K after calibration Voltage 0x09 This read only word returns the cell pack voltage mV Output unsigned integer Returns the battery ter minal voltage in mV Units mV Range 0 to 65 535mV Granularity 0 2 of DesignVoltage Accuracy 1 of DesignVoltage after calibration Current 0x0a This read only word returns the current through the battery s terminals mA Output signed integer Returns the charge dis charge rate in mA where positive is for charge and negative is for discharge Units mA Range 0 to 32 767mA for charge or 0 to 32 768mA for discharge Granularity 0 2 of the DesignCapacity or better Accuracy 1 of the DesignCapacity
14. is 5 The 5 byte charac ter string contains the battery s chemistry For example if the DeviceChemistry function returns NiMH the battery pack contains nickel metal hydride cells Output string or ASCII character string ManufacturerData 0x23 This read only string allows access to an up to 5 byte manufacturer data string Output block data data whose meaning is as signed by the Smart Battery s manufacturer bq2040 End of Discharge Voltage1 0x3e This read only word returns the first end of discharge voltage programmed for the pack Output two s complemented unsigned integer Returns battery end of discharge voltage pro grammed in EEPROM in mV End of Discharge VoltageF 0x3f This read only word returns the final end of discharge voltage programmed for the pack Output two s complemented unsigned integer Returns battery final end of discharge voltage pro grammed in EEPROM in mV FLAGS1 amp 2 0x2f This read only register returns an unsigned integer rep resenting the internal status registers of the bq2040 The MSB represents FLAGS2 and the LSB represents FLAGS1 See Table 6 for the bit description for FLAGS1 and FLAGS2 FLAGS2 The Display Mode flag DMODE bit 7 determines whether the bq2040 displays Relative or Absolute capac ity The DMODE value is FLAGS2 Bits 4 3 7 DMODE Where DMODE is 0 1 Selects Absolute display S
15. left Units minutes Range 0 to 65 534min Granularity 2min or better Invalid data indication 65 535 indicates battery is not being discharged AverageTimeToEmpty 0x12 This read only word returns the predicted remaining battery life at the present average discharge rate min utes The AverageTimeToEmpty is calculated based on AverageCurrent 15 bq2040 Output unsigned integer Returns the minutes of operation left Units minutes Range 0 to 65 534min Granularity 2min or better Invalid data indication 65 535 indicates battery is not being discharged AverageTimeToFull 0x13 This read only word returns the predicted time until the Smart Battery reaches full charge at the present aver age charge rate minutes Output unsigned integer Returns the remaining time in minutes to full Units minutes Range 0 to 65 534min Granularity 2min or better Invalid data indication 65 535 indicates battery is not being charged ChargingCurrent 0x14 If enabled the bq2040 sends the desired charging rate in mA to the Smart Battery Charger Output unsigned integer Transmits returns the maximum charger output current in mA Units mA Range 0 to 65 534mA Granularity 0 2 of the design capacity or better Invalid data indication 65 535 indicates that the Smart Charger should operate as a voltage source outside its maximum regulated current range Charging Voltage 0x15 If enabled the
16. string E Note 1 Defaults after reset or power up 12 Table 4 bq2040 Register Functions Continued bq2040 Function Code Access Units Defaults DeviceChemistry 0x22 read string E ManufacturerData 0x23 read string E FLAG1 and FLAG2 Ox2f read bit flags E End of Discharge Voltage 1 EDV1 Ox8e read E aR ais J Voltage Final Ox3f read E2 Note 1 Defaults after reset or power up 13 bq2040 When the AtRate value is positive the AtRateTimeToF ull function returns the predicted time to full charge at the AtRate value of charge When the AtRate value is negative the AtRateTimeToEmpty function returns the predicted operating time at the AtRate value of discharge Input Output signed integer AtRate is positive for charge and negative for discharge Units mA Range 32 768mA to 32 767mA AiRateTimeToFull 0x05 This read only word returns the predicted remaining time to fully charge the battery at the AtRate value mA and is valid only if read immediately after an AtRate command Output unsigned integer Returns the predicted time to full charge Units minutes Range 0 to 65 534min Granularity 2 min or better Invalid Data Indication 65 535 indicates that the AtRate value is negative AtRateTimeToEmpty 0x06 This read only word returns the predicted remaining op erating time if the battery is discharged at the AtRate value and is valid only if read
17. 0V or the Discharging flag is set m Low Temperature When the battery temperature is less than 12 C LTF bit in FLAGS2 set the requested charge current is set to the maintenance rate Once the temperature is above 15 C the requested charge current is set to the fast rate m Undervoltage When the battery voltage is below the EDVF threshold the requested charge current is set to the EDVF rate stored in EE0x5a 0x5b Once the voltage is above EDVF the requested charge current is set to the fast or maintenance rate depending on the state of the LTF bit bq2040 Count Compensations Charge activity is compensated for temperature and state of charge before updating the RM and or DCR Self discharge estimation is compensated for tempera ture before updating RM or DCR Charge Compensation Charge efficiency is compensated for state of charge temperature and battery chemistry The charge effi ciency is adjusted using the following equations 1 RM RM A Qrrc Qrr where RelativeStateOfCharge lt FullChargePercentage and Q prc is the programmed fast charge efficiency vary ing from 0 75 to 1 0 2 RM RM Qer Qer where RelativeStateOfCharge gt FullChargePercentage and Qgrc is the programmed maintenance trickle charge efficiency varying from 0 75 to 1 0 Q pr is used to adjust the charge efficiency as the battery temperature increases according to the following Qer if T lt 30 C Qer 002 if 30 C l
18. 0mV Used to set the fast charge voltage for the Smart Charger Battery status Ox0c Ox0d 80 00 128 Initializes BatteryStatus Cycle count Ox0e oxof 00 00 0 Contains the charge cycle count and can be set to zero for a new battery Design capacity 0x10 0x11 60 09 2400mAh Normal battery pack capacity Design voltage 0x12 0x13 40 38 14400mV_ Nominal battery pack voltage Specification 0x14 0x15 10 00 1 0 Default value for this register in a 1 0 part information Monuiacimre 0x16 0x17 al 20 May 1 1996 Packed per the ManufactureDate description date 8353 Serial number 0x18 0x19 12 27 10002 Contains the optional pack serial number Fast charging Oxia Oxlb 60 09 2400mA Used to set the fast charge current for the Smart current Charger Maintenance Contains the desired maintenance current after fast charge current Cele Oxld 00 o9 Oma charge termination by the bq2040 Reserved Oxle Ox1f 00 00 0 Must be programmed to 0x00 Current Ox2c Ox2d 70 17 6000mA Sets the discharge current at which EDV threshold overload monitoring is disabled Sets the battery capacity that RemainingCapacity is Battery low 0x2e 08 3 reduced to at EDV1 The value equals 2 56 RM at EDV1 23 bq2040 Table 10 Example Register Contents Continued EEPROM EEPROM Hex Address Contents Low High Low High Example Description Byte Byte Byte B
19. 64 bits NA Li Ion taper current 0x38 0x39 eee oie limit othe taper eee 16 bits mA Maximum overcharge limit 0x8a 0x3b Sets the maximum amount of overcharge 16 bits NA Reserved 0x3c Reserved must 0x00 8 bits NA Access protect 0x3d__ Locks commands outside of the SBS data set 8 bits NA FLAGS1 0x3e Initializes FLAGS1 8 bits NA FLAGS2 Ox8f Initializes FLAGS2 8 bits NA Device chemistry 0x40 0x45 Programs DeviceChemistry 0x22 48 bits NA Current measurement gain 0x46 0x47 Sense resistor calibration value 16 bits NA Battery voltage offset 0x48 Voltage calibration value 8 bits NA Temperature offset 0x49 Temperature calibration value 8 bits NA Maximum temperature and 0x4a Sets the maximum charge temperature and the AT 8 bits NA Table 1 Configuration Memory Map Continued bq2040 Parameter Name Address Description Length Units Charge efficiency 0x4b Sets the high low charge rate efficiencies 8 bits NA Full charge percentage Ox4c ena ST ae which the battery is consid 8 bits NA Digitial filter Ox4d Sets the minimum charge discharge threshold 8 bits NA Current integration gain Ox4e Raa cain Aen integration gain to the 8 bits NA Self discharge rate 0x4f Sets the battery s self discharge rate 8 bits NA Manufacturer data 0x50 0x55 Programs ManufacturerData 0x23 48 bits NA Voltage gain1 0x56 0x57 Battery divider calibration value 16 bits NA Reserved 0x58 0x59 Reserved 16
20. Alarm 0x02 This function sets or returns the low remaining time alarm value When the AverageTimeToEmpty falls be low this value the Remaining Time Alarm bit in Bat teryStatus is set The default value for this register is programmed in EE 0x02 0x03 The system may alter this alarm during operation 11 Input Output unsigned integer This sets returns the value where the Remaining_Time_Alarm bit is set in Battery Status Units minutes Range 0 to 65 535 minutes Battery Mode 0x03 This read write word selects the various battery opera tional modes The bq2040 supports the battery capacity information specified in mAh This function also deter mines whether the bq2040 charging values are broad casted to the Smart Battery Charger address Writing bit 14 to 1 disables voltage and current Master Mode broadcasts to the Smart Battery Charger Bit 14 is automatically reset to 0 if SMBC and SMBD 0 for greater than 2 seconds i e pack removal Writing bit 13 to 1 disables all Master Mode broadcasts including alarm messages to the Smart Battery Charger and Host The bit remains set until overwritten Pro gramming bit 3 of FLAGS2 in the EEPROM EE0x38f initializes this bit to a 1 Bit 7 is the condition request flag It is set when the bq2040 is initialized from the EEPROM and reset when a learning cycle has been completed It is also set to a 1 if CycleCount increases by 32 without a new learning cycle AtRate
21. F is set when Temperature is lt 12 C and cleared when Temperature is gt 15 C The LTF value is FLAGS2 Bits 4 3 LTF Where LTF is 0 1 Temperature gt 15 C Temperature lt 12 C Bit 0 the Overcurrent flag OC is set when Current is 25 greater than the programmed charging current If the charging current is programmed less than 1024mA overcurrent is set if Current is 256mA greater than the programmed charging current This flag is cleared when Current falls below 256mA The OC value is FLAGS2 Bits 7 6 5 4 3 2 1 0 OC Where OC is 0 Current is less than 1 25 ChargingCur rent or less than 256mA if charging current is programmed less than 1024mA Current exceeds 1 25 ChargingCurrent or 256mA if the charging current is pro grammed less than 1024mA This bit is cleared if Current lt 256mA FLAGS1 Bits 7 indicates that a AT At termination condition exists The AT At value is FLAGS1 Bits 7 6 5 4 3 2 1 0 ADA r Z Where AT At is 0 The AT At rate drops below the pro grammed rate 1 The AT At rate exceeds the programmed rate Bit 6 indicates that a current taper termination condi tion exists bq2040 The Im value is Where Imin is 0 A valid current taper termination condition is not present 1 Valid current taper termination condition
22. NA EEPROM check1 0x01 EEPROM data integrity check byte must 0x5b 8 bits NA Remaining time alarm 0x02 0x03 Sets RemainingTimeAlarm 0x02 16 bits minutes Remaining capacity alarm 0x04 0x05 Sets RemainingCapacityAlarm 0x01 16 bits mAh Reserved 0x06 0x07 Reserved for future use 16 bits NA Initial charging current 0x08 0x09 Sets the initial charging current 16 bits mA Charging voltage 0x0a 0x0b Sets ChargingVoltage 0x15 16 bits mV Battery status 0x0c 0x0d Initializes BatteryStatus 0x16 16 bits NA Cycle count 0x0e 0x0f Initializes and stores CycleCount 0x17 16 bits cycles Design capacity 0x10 0x11 Sets DesignCapacity 0x18 16 bits mAh Design voltage 0x12 0x13 Sets DesignVoltage 0x19 16 bits mV Specification information 0x14 0x15 Programs SpecificationInfo 0x1la 16 bits NA Manufacture date 0x16 0x17 Programs ManufactureDate 0x1b 16 bits NA Serial number 0x18 0x19 Programs SerialNumber 0x1c 16 bits NA Fast charging current 0x1a 0x1b Sets ChargingCurrent 0x14 16 bits mA Maintenance charge current 0x1c 0x1d Sets the trickle current request 16 bits mA Reserved 0x1e 0x1f Reserved must 0x0000 16 bits mAh Manufacturer name 0x20 0x2b Programs ManufacturerName 0x20 96 bits NA Current overload 0x2c 0x2d Sets the overload current threshold 16 bits mA Battery low 0x2e Sets the battery low amount 8 bits Reserved Ox2f Reserved for future use 8 bits NA Device name 0x30 0x37 Programs DeviceName 0x21
23. O 0 BQ2040 0 O s Benchmarg Products from Texas Instruments bq2040 Gas Gauge IC With SMBus Interface Features gt Provides accurate measurement of available charge in NiCd NiMH and Li Ion batteries gt Supports SBS v1 0 data set and two wire interface gt Monitors charge FET in Li Ion pack protection circuit gt Designed for battery pack inte gration Low operating current Complete circuit can fit on less than square inch of PCB space gt Supports SBS charge control commands for NiCd NiMH and Li Ion Drives a four segment LED dis play for remaining capacity indication gt 16 pin narrow SOIC General Description The bq2040 Gas Gauge IC With SMBus Interface is intended for battery pack or in system installa tion to maintain an accurate record of available battery charge The bq2040 directly supports capacity monitoring for NiCd NiMH and Li Ion battery chemistries The bq2040 uses the System Man agement Bus v1 0 SMBus protocol and supports the Smart Battery Data SBData commands The bq2040 also supports the SBData charge control functions Battery state of charge remaining capacity remaining time and chemistry are available over the serial link Battery charge state can be directly indicated using a four segment LED display to graphically depict battery full to empty in 25 increments The bq2040 estimates battery self discharge based on an internal timer and temp
24. Voltage gt EDV1 Current lt programmed rate FLAGS 1 Bits 7 6 5 4 3 2 1 0 EDV1 The EDV1 value is Where EDV1 is 0 VQ 1and Voltage gt EDV1 1 Voltage lt EDV1 and OVLD 0 The Final End of Discharge Voltage flag EDVF bit 0 is set when Voltage lt EDVF and OVLD 0 and cleared when VQ 1 and Voltage gt EDVF FLAGS 1 Bits 7 6 5 4 3 2 1 0 EDVF The EDVF value is Where EDVF is 0 VQ 1and Voltage gt EDVF 1 Voltage lt EDVF and OVLD 0 Error Codes and Status Bits Error codes and status bits are listed in Table 8 and Ta ble 9 respectively 20 SBD Seal The bq2040 address space can be locked to enforce the SBS specified access to each command code To lock the address space the bq2040 must be initialized with EE Ox8d set to bOh Once this is done only commands 0x00 0x04 may be written Attempting to write to any other address will cause a no acknowledge of the data Reading will only be permitted from the command codes listed in the SBD specification plus the five locations designated as optional manufacturing functions 1 5 Ox2f 0x3c 0x3f Programming the bq2040 The bq2040 requires the proper programming of an ex ternal EEPROM for proper device operation Each mod ule can be calibrated for the greatest accuracy or gen eral default values can be used An EV2200 40 pro g
25. and Li Ion chemistries The bq2040 uses current taper detection for Li Ion primary charge termi nation and AT At for nickel based primary charge termi nation The bq2040 also provides a number of safety terminations based on battery capacity voltage and temperature Current Taper For Li Ion charge control the ChargingVoltage must be set to the desired pack voltage during the constant volt age charge phase The bq2040 detects a current taper termination when it measures the pack voltage to be within 128mV of the requested charging voltage and when the AverageCurrent is less than the programmed threshold in EE 0x38 0x39 and non zero for at least 100s AT At The AT At used by the bq2040 is programmable in both the temperature step 1 6 C 4 6 C and time step 20 seconds 320seconds Typical settings for 1 C min in clude 2 C over 120 seconds and 3 C over 180 seconds Longer times are required for increased slope resolution AL is set by the formula ere At At dower nibble of EE 0x4a 2 16 10 320 EE 0x62 20 s In addition to the AT At timer there is a hold off timer which starts when the battery is being charged at more than 255mA and the temperature is above 25 C Until this timer expires AT At is suspended If the tempera ture falls below 25 C or if charging current falls below 255mA the timer is reset and restarts only if these con ditions are once again within range The hold off tim
26. arge threshold counting continues until Vsro falls be low Vsrp Vsrp is a programmable threshold as de scribed in the Digital Magnitude Filter section Discharge Counting All discharge counts where Vsro lt Vsrp cause the RM register to decrement and the DCR to increment Vsrp is a programmable threshold as described in the Digital Magnitude Filter section Self Discharge Estimation The bq2040 continuously decrements RM and incre ments DCR for self discharge based on time and temper ature provided that the discharge flag in BatteryStatus is set charge not detected The bq2040 self discharge estimation rate is programmed in EE 0x4f and can be set from 0 to 25 per day for 20 30 C This rate approx imately doubles for every 10 C increase until the tem perature is gt 70 C or halves every 10 C decrease until the temperature is lt 10 C Charge Control The bq2040 supports SBS charge control by broadcast ing the ChargingCurrent and the ChargingVoltage to the Smart Charger address The bq2040 broadcasts charging commands every 10 seconds the broadcasts can be disabled by writing bit 14 of BatteryMode to 1 On reset the initial charging current broadcast to the charger is set to the value programmed in EE 0x08 0x09 The bq2040 updates the value used in the charg ing current broadcasts based on the battery s state of charge voltage and temperature The bq2040 internal charge control is compatible with nickel based
27. ay drive an external LED Ground Sense resistor input The voltage drop Vsr across pins SR and Vss is monitored and integrated over time to interpret charge and discharge activity The SR input is connected to the sense re sistor and the negative terminal of the battery Vsr lt Vss indicates discharge and Vsr gt Vss indicates charge The effective voltage drop Vsro as seen by the bq2040 is Vsr Vos See Table 3 DISP SB PSTAT SMBD SMBC REF Vout Display control input DISP high disables the LED display DISP floating allows the LED display to be active during charge if the rate is greater than 100mA DISP low activates the display for 4 seconds Secondary battery input Monitors the pack voltage through a high impedance resistor divider network The pack voltage is reported in the SBD register function Voltage 0x09 and is monitored for end of discharge voltage and charging volt age parameters Protector status input Provides overvoltage status from the Li Ion protector circuit and can initiate a charge sus pend request SMBus data Open drain bidirectional pin used to transfer address and data to and from the bq2040 SMBus clock Open drain bidirectional pin used to clock the data transfer to and from the bq2040 Reference output for regulator REF provides a reference output for an op tional FET based micro regulator Supply output Supplies power to the external EEPROM con
28. bits NA EDVF charging current 0x5a 0x5b a no aaa When the battery 16 bits NA End of discharge voltage1 0x5c 0x5d Sets EDV1 16 bits NA End of discharge voltage final 0x5e 0x5f Sets EDVF 16 bits NA Full charge capacity 0x60 0x61 Initializes and stores FullChargeCapacity 0x10 16 bits mAh At step 0x62 Sets the At step for AT At termination 8 bits NA Hold off time 0x63 Sets AT At hold off timer 8 bits NA EEPROM check 2 ae 8bits NA Reserved 0x65 0x7f Reserved for future use NA bq2040 Voltage Thresholds In conjunction with monitoring Vsr for charge discharge currents the bq2040 monitors the battery potential through the SB pin The voltage potential is deter mined through a resistor divider network per the fol lowing equation MBV R 22 where MBV is the maximum battery voltage Rs is con nected to the positive battery terminal and R4 is con nected to the negative battery terminal R5 R4 should be rounded to the next higher integer The voltage at the SB pin Vsp should never exceed 2 4V The battery voltage is monitored for the end of discharge voltages EDV1 and EDVF and for alarm warning conditions EDV threshold levels are used to de termine when the battery has reached a programmable empty state The bq2040 generates an alarm warning when the battery voltage exceeds the maximum charg ing voltage by 5 or if the voltage is below EDVF The battery voltage gain the two EDV thresholds and th
29. bq2040 sends the desired voltage in mV to the Smart Battery Charger Output unsigned integer Transmits returns the charger voltage output in mV Units mV Range 0 to 65 534mV Granularity 0 2 of the DesignVoltage or better Invalid data indication 65 535 indicates that the Smart Battery Charger should operate as a cur rent source outside its maximum regulated voltage range 16 BatteryStatus 0x16 This read only word returns the battery status word Output unsigned integer Returns the status reg ister with alarm conditions bitmapped as shown in Table 5 Some of the BatteryStatus flags Remaining Capac ity_Alarm and Remaining Time Alarm are calculated based on current See Table 8 and 9 for definitions Table 5 Status Register Alarm Bits 0x8000 Over_Charged_Alarm 0x4000 Terminate_Charge_ Alarm 0x2000 Reserved 0x1000 Over_Temp_Alarm 0x0800 Terminate_Discharge Alarm 0x0400 Reserved 0x0200 Remaining Capacity_Alarm 0x0100 Remaining Time Alarm Status Bits 0x0080 Initialized 0x0040 Discharging 0x0020 Fully_Charged 0x0010 Fully_Discharged Error Code rie ie Reserved for error codes CycleCouni 0x17 This read only word returns the number of charge dis charge cycles the battery has experienced A charge dis charge cycle starts from a base value equivalent to the battery s state of charge on completion of a charge cycle The bq2040 increments the cycle counte
30. discharges from full to empty will minimize er rors in FCC Current Sensing Error Table 3 illustrates the current sensing error as a func tion of Vsr A digital filter eliminates charge and dis charge counts to the RM register when Vsrp lt Vsro lt VSRD Display The bq2040 can directly display capacity information us ing low power LEDs The bq2040 displays the battery charge state in either absolute or relative mode In rela tive mode the battery charge is represented as a per centage of the FCC Each LED segment represents 25 of the FCC In absolute mode each segment represents a fixed amount of charge 25 of the DesignCapacity As the battery wears out over time it is possible for the FCC to be below the design capacity In this case all of the LEDs may not turn on in absolute mode representing the reduction in the actual battery capacity When DISP is tied to Vcc the LED1 4 outputs are inac tive When DISP is left floating the display becomes ac tive whenever the bq2040 detects a charge rate of 100mA or more When pulled low the segment outputs become active immediately for a period of approximately 4 seconds The DISP pin must be returned to float or Vcc to reactivate the display LED blinks at a 4Hz rate indicating a low battery con dition whenever the display is active EDVF is not set 10 and Remaining Capacity_Alarm is set Vsp below EDVF EDVF 1 disables the display output Microre
31. e charging voltage are programmable in the EEPROM If Vsp is below either of the two EDV thresholds the associ ated flag is latched and remains latched independent of Vsp until the next valid charge EDV monitoring may be disabled under certain condi tions If the discharge current is greater than the value stored in location 0x2c and 0x2d in the EEPROM EE 0x2c 0x2d EDV monitoring is disabled and resumes af ter the current falls below the programmed value Reset The bq2040 is reset when first connected to the battery pack On power up the bq2040 initializes and reads the EEPROM configuration memory The bq2040 can also be reset with a command over the SMBus The software reset sequence is the following 1 write MaxError 0x0c to 0x0000 2 write the reset register 0x64 to 0x8009 A software reset can only be performed if the bq2040 is in an unlocked state as defined by the value in location 0x3d of the EEPROM EE 0x3d on power up Temperature The bq2040 monitors temperature sensing using an in ternal sensor The temperature is used to adapt charge and self discharge compensations as well as to monitor for maximum temperature and AT At during a bq2040 controlled charge Temperature may also be accessed over the SMBus with command 0x08 Layout Considerations The bq2040 measures the voltage differential between the SR and Vss pins Vos the offset voltage at the SR pin is greatly affected by PC board layout For op
32. e is programmed in EE 0x63 Charge Termination Once the bq2040 detects a valid charge termination the Fully_Charged Terminate_Charge_Alarm and the Over_Charged_Alarm bits are set in BatteryStatus and the requested charge current is set to zero Once the terminating conditions cease the Termi nate_Charge Alarm and the Over_Charged_Alarm are cleared and the requested charging current is set to the maintenance rate The bq2040 requests the mainte nance rate until RM falls below the amount determined by the programmable full charge percentage Once this occurs the Fully_Charged bit is cleared and the re quested charge current and voltage are set to the fast charge rate Bit 4 CC in FLAGS2 determines whether RM is modi fied after a AT At or current taper termination occurs If CC 1 RM may be set from 0 to 100 of the FullChar geCapacity as defined in EE 0x4c If RM is below the full charge percentage RM is set to the full charge per centage of FCC If RM is above the full charge percent age RM is not modified Charge Suspension The bq2040 may temporarily suspend charge if it detects a charging fault The charging faults include the follow ing conditions a Maximum Overcharge If charging continues for more than the programmed maximum overcharge limit as defined in EE 0x3a 0x3b beyond RM FCC the Fully_Charged bit is set and the requested charging current is set to the maintenance rate m Overvoltage An over
33. e stop and 4 7 us ESTA PAES after repeated start 40 us TSU STA Repeated start condition setup time 4 7 us Tsu sto Stop condition setup time 4 0 us THD DAT Data hold time 300 ns TSU DAT Data setup time 250 ns TLow Clock low period 4 7 us THIGH Clock high period 4 0 us TF Clock data fall time 300 ns TR Clock data rise time 1000 ns Tienes Cumulative clock low extend time 25 ms slave TTIMEOUT 25 35 ms Bus Timing Data SMBC SMBD 29 TD294501 eps bq2040 16 Pin SOIC Narrow SN 16 Pin SN SOIC Narrow 9 Dimension Minimum Maximum fi p l gt o A 0 060 0 070 F D B 4 3 A1 0 004 0 010 i e q B 0 013 0 020 f 1 ch C 0 007 0 010 z LEP D 0 385 0 400 E 0 150 0 160 E e 0 045 0 055 i H eee H 0 225 0 245 L 0 015 0 035 All dimensions are in inches A l A1 A R Ep T A 004 30 bq2040 Data Sheet Revision History ChangeNo Page No Description of Change 3 3 Updated recommended application schematic 3 9 Changed overcurrent fault conditon for ChargingCurrent lt 1024mA 3 10 4Hz operation of LED clarification 3 11 Added descriptions for bits 7 and 13 of BatteryMode 3 14 AtRateTimeToEmpty and AtRateTimeToFull invalid data indication correction 3 15 16 RunTimeToEmpty AverageTimeToEmpty and Av
34. eger word The date is packed as follows year 1980 512 month 32 day Bits Field Used Format Allowable Value 5 bit binary 1 31 corresponds to Day 0 4 value date Month 5 8 4 bit binary 1 12 corresponds to value month number 7 bit binary 0 127 corresponds to Year 9 15 value year biased by 1980 17 This read only word returns a serial number This number when combined with the ManufacturerName the DeviceName and the ManufactureDate uniquely identifies the battery Output unsigned integer ManufacturerName 0x20 This read only string returns a character string where the first byte is the number of characters available The maxi mum number of characters is 11 The character string con tains the battery manufacturer s name For example Benchmargq identifies the battery pack manufacturer as Benchmargq Output string or ASCII character string DeviceName 0x21 This read only string returns a character string where the first byte is the number of characters available The maxi mum number of characters is 7 The 7 byte character string contains the battery s name For example a DeviceName of bq2040 indicates that the battery is a model bq2040 Output string or ASCII character string DeviceChemisiry 0x22 This read only string returns a character string where the first byte is the number of characters available The maximum number of characters
35. elects Relative display Bit 6 reflects the high low state of PSTAT PSTAT 21 5V generates a charge suspend condition The PSTAT value is FLAGS2 Bits 7 6 5 4 3 2 1 0 PSTAT Where PSTAT is 0 PSTAT input lt 1 0V 1 PSTAT input gt 1 5V The Chemistry flag CHM bit 5 selects Li Ion or nickel compensation factors 18 The CHM value is FLAGS2 Bits 7 6 5 4 3 2 1 0 CHM Where CHM is 0 Selects Nickel 1 Selects Li Ion Bit 4 the Charge Control flag CC determines whether a bq2040 based charge termination will set RM to a user defined programmable full charge capacity The CC value is FLAGS2 Bits 7 6 5 4 3 2 1 0 B 3 3 cc p p Where CC is 0 RMis not modified on valid bq2040 charge termination 1 RMis set to a programmable percentage of the FCC when a valid bq2040 charge termi nation occurs Bit 3 is reserved Bit 2 the Overvoltage flag OV is set when the bq2040 detects a pack voltage 5 greater than the programmed charging voltage This bit is cleared when the pack volt age falls 5 below the programmed charging voltage The OV value is FLAGS2 Bits 7 6 5 4 3 2 1 0 z a z a OV Where OV is 0 Voltage lt 1 05 ChargingVoltage 1 Voltage gt 1 05 x ChargingVoltage Bit 1 the Low Temperature Fault flag LT
36. erageTimeToFull invalid data j indication corrections 3 23 Changed typical Battery low value for Li Ion with EDV1 3 0V cell 3 24 Li Ion taper current is stored in 2 s complement 3 24 Changed typical AT step and Full charge percentage for Li Ion 3 25 Voltage gain is R4 R5 R4 3 25 Changed typical EDV1 and EDVF values for Li Ion 4 6 Added Vsg should not exceed 2 4V 4 8 The self discharge rate approximated y doubles or halves 4 11 Changed cycle count increase from 30 to 32 for condition request 4 14 Changed AtRateOK indication from EDV1 to EDVF 4 25 Changed self discharge programming from 52 75 x to 52 73 x 4 25 Changed recommended EDVF charging current from 0mA to 100mA Notes Changes 1 and 2 refer to the 1998 Data Book Change 3 June1998 D changes from Jan 1998 C Change 4 June 1999 E changes from June 1998 D Ordering Information bq2040 Temperature Range blank Commercial 0 to 70 C Package Option SN 16 pin narrow SOIC Device bq2040 Gas Gauge IC With SMBus Interface 31 K Texas PACKAGE OPTION ADDENDUM INSTRUMENTS www ti com 8 Mar 2005 PACKAGING INFORMATION Orderable Device Status Package Package Pins Package Eco Plan Lead Ball Finish MSL Peak Temp Type Drawing Qty BQ2040SN C408 NRND SOIC D 16 40 None CU NIPDAU Level 1 220C UNLIM BQ2040SN C408TR NRND SOIC D 16 2500 None CU NIPDAU Level 1 220C UNLIM BQ2040SN D111 ACTIVE SOIC D 16 40 None CU NIPDAU
37. erature sensor and user programmable rate informa tion stored in external EEPROM The bq2040 also automatically re calibrates or learns battery capac ity in the full course of a discharge cycle from full to empty The bq2040 may operate directly from three nickel chemistry cells With the REF output and an exter nal transistor a simple inexpensive regulator can be built to provide Vcc for other battery cell configu rations An external EEPROM is used to program initial values into the bq2040 and is necessary for proper operation Pin Connections Vcc ESCL ESDA LED LED LED3 LED4 Vss 16 Pin Narrow SOIC PN204001 eps SLUS005 JUNE 1999 E Pin Names Vec 3 0 6 5V ESCL EEPROM clock ESDA EEPROM data LED 4 LED segment 1 4 Vss System ground SR Sense resistor input DISP Display control input SB Battery sense input PSTAT Protector status input SMBD SMBus data input output SMBC SMBus clock REF Voltage reference output Vour EEPROM supply output bq2040 Pin Descriptions Vcc ESCL ESDA LED LED Vss SR Supply voltage input Serial memory clock Output used to clock the data transfer be tween the bq2040 and the external non volatile configuration memory Serial memory data and address Bidirectional pin used to transfer address and data to and from the bq2040 and the ex ternal nonvolitile configuration memory LED display segment outputs Each output m
38. erefore the bq2040 adapts its capacity determination based on the actual condi tions of discharge The battery s initial full capacity is set to the value stored in EE 0x60 0x61 Until FCC is updated RM counts up to but not beyond this threshold during subsequent charges The battery s empty state is also programmed in the EEPROM The battery low percentage EE 0x2e stores the percentage of FCC that will be written to RM when the battery voltage drops below the EDV1 threshold 1 FullChargeCapacity or learned battery capacity FCC is the last measured discharge capacity of the battery On initialization application of Vcc or reset FCC is set to the value stored in the EEPROM Dur bq2040 Charge Inputs Current State of charge and Temperature Compensation Main Counters and Capacity RM Reference FCC Discharge Remaining Capacity Self Discharge Current Timer Temperature Compensation Full Discharge Charge Count Capacity Qualified Register FCC Transfer DCR Temperature Other Data Chip Controlled Two Wire Outputs Available Charge Serial Interface LED Display FG294501 eps Figure 2 Operational Overview ing subsequent discharges FCC is updated with the latest measured capacity in the Discharge Count Reg ister plus the battery low amount representing a dis charge from full to below EDV1 A qualified dis charge is necessary for a capacity
39. ght 3 MSL Peak Temp The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications and peak solder temperature Important Information and Disclaimer The information provided on this page represents TI s knowledge and belief as of the date that it is provided Tl bases its knowledge and belief on information provided by third parties and makes no representation or warranty as to the accuracy of such information Efforts are underway to better integrate information from third parties TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals TI and TI suppliers consider certain information to be proprietary and thus CAS numbers and other limited information may not be available for release In no event shall TI s liability arising out of such information exceed the total purchase price of the TI part s at issue in this document sold by TI to Customer on an annual basis Addendum Page 1 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries Tl reserve the right to make corrections modifications enhancements improvements and other changes to its products and services at any time and to discontinue any product or service without notice Customers should obtain the latest relevant information before placing orders and should verify that such
40. gulator The bq2040 can operate directly from three nickel chem istry cells To facilitate the power supply requirements of the bq2040 an REF output is provided to regulate an external low threshold n FET A micropower source for the bq2040 can be built inexpensively using a 2N7002 or BSS138 FET and an external resistor See Figure 1 The value of R11 depends on the battery pack s nominal voltage Communicating With the bq2040 The bq2040 includes a simple two pin SMBC and SMBD bi directional serial data interface A host proc essor uses the interface to access various bq2040 regis ters see Table 4 This method allows battery character istics to be monitored easily The open drain SMBD and SMBC pins on the bq2040 are pulled up by the host sys tem or may be connected to Vss if the serial interface is not used The interface uses a command based protocol where the host processor sends the battery address and an eight bit command byte to the bq2040 The command directs the bq2040 to either store the next data received to a register specified by the command byte or output the data specified by the command byte bq2040 Data Protocols The host system acting in the role of a Bus master uses the read word and write word protocols to communicate integer data with the bq2040 See Figure 3 Host to bq2040 Message Protocol The Bus Host communicates with the bq2040 using one of three protocols m Read word a Write word
41. harge is only valid for battery capacities more than 1504mAh and less than 10 400mAh Output unsigned integer Returns the percent of remaining capacity Units Range 0 to 65 535 Granularity 1 Accuracy MaxError after circuit and capacity calibration bq2040 RemainingCapacity 0x0f This read only word returns the predicted remaining battery capacity The RemainingCapacity value is ex pressed in mAh Output unsigned integer Returns the estimated re maining capacity in mAh Units mAh Range 0 to 65 535mAh Granularity 0 2 of DesignCapacity or better Accuracy t MaxError FCC after circuit and ca pacity calibration FullChargeCapacity 0x10 This read only word returns the predicted pack capacity when it is fully charged FullChargeCapacity defaults to the value programmed in the external EEPROM until a new pack capacity is learned The new FCC is stored to EEPROM within 400ms of a valid charge after a qualified discharge Output unsigned integer Returns the estimated full charge capacity in mAh Units mAh Range 0 to 65 535mAh Granularity 0 2 of DesignCapacity or better Accuracy MaxError FCC after circuit and ca pacity calibration RunTimeToEmpty 0x11 This read only word returns the predicted remaining battery life at the present rate of discharge minutes The RunTimeToEmpty value is calculated based on Current Output unsigned integer Returns the minutes of operation
42. information is current and complete All products are sold subject to Tl s terms and conditions of sale supplied at the time of order acknowledgment Tl warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with Tl s standard warranty Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty Except where mandated by government requirements testing of all parameters of each product is not necessarily performed TI assumes no liability for applications assistance or customer product design Customers are responsible for their products and applications using TI components To minimize the risks associated with customer products and applications customers should provide adequate design and operating safeguards TI does not warrant or represent that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or other intellectual property of the third party or a license from TI under the patents or other inte
43. llectual property of TI Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties conditions limitations and notices Reproduction of this information with alteration is an unfair and deceptive business practice TI is not responsible or liable for such altered documentation Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice TI is not responsible or liable for any such statements Following are URLs where you can obtain information on other Texas Instruments products and application solutions Products Applications Amplifiers amplifier ti com Audio www ti com audio Data Converters dataconverter ti com Automotive www ti com automotive DSP dsp ti com Broadband www ti com broadband Interface interface ti com Digital Control www ti com digitalcontrol Logic logic ti com Military www ti com military Power Mgmt power ti com Optical Networking www ti com opticalnetwork Microcontrollers microcontroller ti com Security www ti com security Telephony www ti com telephony Video amp Imaging www ti com video Wireless www ti com wireless Mailing Address Texas Instruments Post Office Box 655303 Dallas Texas 75265 Copyright
44. p eae dT lower nibble AT step 4 6 C Maintenance Sets the fast charge high and maintenance charge Ch compensation low efficiencies The upper nibbles sets the low effi ads 0x4b ff 100 ciency and the lower nibble adjusts the high effi Eh Fast compensa ciency according to the equation tion 100 Nibble efficiency 256 196 4 This packed field is the two s complement of the de Full char sired value in RM when the bq2040 determines a ky ia ge Ox4c 9c 100 full charge termination If RM is below this value percentage s RM is set to this value If RM is above this value then RM is not adjusted Note 1 Can be adjusted to calibrate the battery pack 24 bq2040 Table 10 Example Register Contents Continued EEPROM EEPROM Hex Address Contents x 7 Example aini Low High Low High Description Byte Byte Byte Byte Values Notes Digital filter Ox4d 96 0 30mV Used to set the digital magnitude filter as described in Table 2 Represents the following 3 2 sense resistor in ohms C rrentintezra It is used by the bq2040 to scale the measured voltage ti 8 Ox4e 40 0 3 2 0 05 values on the SR pin in mA and mAh This register ion gain vee also compensates for variations in the reported sense resistor value This packed field is the two s complement of 52 73 x Self discharge rate 0x4f 2d 0 25 where x is the desired self
45. r during the cur rent charge cycle if the battery has been discharged 15 below the state of charge at the end of the last charge cy cle This prevents false reporting of small charge discharge cycles The cycle count is stored in EEPROM within 400ms of an update Output unsigned integer Returns the count of charge discharge cycles the battery has experienced Units cycles bq2040 Table 6 Bit Descriptions for FLAGS1 and FLAGS2 MSB 7 6 5 4 3 2 1 0 LSB FLAGS2 DMODE PSTAT CHM CC OV LTF OC FLAGS1 AT At Ian VQ VDQ OVLD EDV1 EDVF Note Reserved Range 0 to 65 535 cycles 65 535 indicates battery SerialNumber 0x1c has experienced 65 535 or more cycles Granularity 1 cycle DesignCapacity 0x18 This read only word returns the theoretical capacity of a new pack The DesignCapacity value is expressed in mAh at the nominal discharge rate Output unsigned integer Returns the battery ca pacity in mAh Units mAh Range 0 to 65 535mAh DesignVoltage 0x19 This read only word returns the theoretical voltage of anew pack in mV Output unsigned integer Returns the battery s normal terminal voltage in mV Units mV Range 0 to 65 535mV SpecificationInfo 0x1a This read only word returns the specification re vision the bq2040 supports ManufactureDate 0x1b This read only word returns the date the cell was manu factured in a packed int
46. ramming kit interface board software and cable for an IBM compatible PC is available from Benchmargq The bq2040 uses a 24LC01 or equivalent serial EE PROM capable of read operation to 2 0V for storing the various initial values calibration data and string infor mation Table 1 outlines the parameters and addresses for this information Tables 10 and 11 detail the various register contents and show an example program value for an 2400mAh 4 series Li Ion battery pack using a 50mQ sense resistor bq2040 Table 8 Error Codes BatteryStatus 0x16 Error Code Access Description OK 0x0000 read write bq2040 processed the function code without detecting any errors Busy 0x0001 read write bq2040 is unable to process the function code at this time ReservedCommand 0x0002 read write a cannot read or write the data at this time try again UnsupportedCommand 0x0003 read write bq2040 does not support the requested function code Access Denied 0x0004 write ea detected an attempt to write to a read only function Overflow Underflow 0x0005 read write bq2040 detected a data overflow or underflow BadSize 0x0006 write bq2040 detected an attempt to write to a function code with an incorrect size data block UnknownError 0x0007 read write bq2040 detected an unidentifiable error Note Reading the bq2040 after an error clears the error code 21 bq2040 Table 9 BatteryStatus Bits
47. t T lt 40 C Qer 0 05 if T gt 40 C 0 Qzt is 0 over the entire temperature range for Li Ion Digital Magnitude Filter The bq2040 has a programmable digital filter to elimi nate charge and discharge counting below a set threshold Vsrp Table 2 shows typical digital filter settings The proper digital filter setting can be calcu lated using the following equation Table 2 Typical Digital Filter Settings DMF DMF Hex Vsrp mV 75 4B 0 60 100 64 0 45 150 96 0 30 175 AF 0 26 200 c8 0 23 bq2040 Table 3 bq2040 Current Sensing Errors Symbol Parameter Typical Maximum Units Notes Vos Offset referred to Vsr 75 150 uV DISP Vcc INL Integrated non linearity 1 4 Add 0 1 per C above or below 25 C error E and 1 per volt above or below 4 25V INR Integrated non 05 1 Measurement repeatability given repeatability error similar operating conditions Error Summary Capacity Inaccurate The FCC is susceptible to error on initialization or if no updates occur On initialization the FCC value includes the error between the design capacity and the actual ca pacity This error is present until a qualified discharge occurs and FCC is updated see the DCR description The other cause of FCC error is battery wear out As the battery ages the measured capacity must be adjusted to account for changes in actual battery capacity Periodic qualified
48. timal results the PC board layout should follow the strict rule of a single point ground return Sharing high current ground with small signal ground causes undesirable noise on the small signal nodes Additionally in refer ence to Figure 1 m The capacitors C1 and C2 should be placed as close as possible to the SB and Vcc pins and their paths to Vss should be as short as possible A high quality ceramic capacitor of 0 1ufis recommended for Vcc m The sense resistor capacitor C3 should be placed as close as possible to the SR pin m The bq2040 should be in thermal contact with the cells for optimum temperature measurement Gas Gauge Operation The operational overview diagram in Figure 2 illus trates the operation of the bq2040 The bq2040 accumu lates a measure of charge and discharge currents as well as an estimation of self discharge Charge currents are compensated for temperature and state of charge of the battery Self discharge is temperature compensated The main counter RemainingCapacity RM represents the available battery capacity at any given time Battery charging increments the RM register whereas battery dis charging and self discharge decrement the RM register and increment the internal Discharge Count Register DCR The Discharge Count Register is used to update the FullChargeCapacity FCC register only if a complete battery discharge from full to empty occurs without any partial battery charges Th
49. transfer from the DCR to the FCC register Once updated the bq2040 writes the new FCC to the EEPROM The FCC also serves as the 100 reference threshold used by the relative state of charge calculation and display DesignCapacity DC The DC is the user specified battery capacity and is programmed from external EEPROM The DC also provides the 100 reference for the absolute dis play mode RemainingCapacity RM RM counts up during charge to a maximum value of FCC and down during discharge and self discharge to 0 RM is set to the battery low amount after the EDV1 threshold has been reached If RM is already equal to or less than the battery low amount RM is not modified If RM reaches the battery low amount before the battery voltage falls below EDV1 on dis charge RM stops counting down until the EDV1 threshold is reached RM is set to 0 when the battery voltage reaches EDVF To prevent overstatement of charge during periods of overcharge RM stops in crementing when RM FCC RM may optionally be written to a user defined value when fully charged if the battery pack is under bq2040 charge control On initialization RM is set to 0 Discharge Count Register DCR The DCR counts up during discharge independent of RM and can continue increasing after RM has decremented to 0 Prior to RM 0 both discharge and self discharge increment the DCR After RM 0 only discharge increments the DCR The DCR resets to 0 when RM FCC
50. unc tion Either the value set by the Remain ingTimeAlarm function is lower than the AverageTimeToEmpty or a valid charge is detected being charged Status Bits Bit Name Set When Reset When INITIALIZED The bq2040 loads from the EEPROM 4 1 4 EEPROM load ia detected bit 7 set in EE0x0c DISCHARGING The bq2040 determines that it is not Battery detects that it is being charged FULLY_CHARGED The bq2040 determines a valid charge termination or a maximum overcharge state RM discharges below the full charge percentage FULLY_DISCHARGED bq2040 determines that it has supplied all the charge that it can without being damaged RelativeStateOfCharge is greater than or equal to 20 22 bq2040 Table 10 Example Register Contents EEPROM EEPROM Address Hex Contents Low High Low High Example Description Byte Byte Byte Byte Values Notes FEEEROM 0x00 64 100 Must be equal to 0x64 length EEPROM check 1 0x01 5b 91 Must be equal to 0x5b Tea time 0x02 0x03 0a 00 10 minutes Sets the low time alarm level Rema ning 0x04 0x05 fo 00 240mAh Sets the low capacity alarm level capacity alarm Reserved 0x06 0x07 00 00 0 Not currently used by the bq2040 Initial charging 0x08 0x09 60 09 2400mA Sets the initial charge request current Charging voltage 0x0a Ox0b d8 40 1660
51. voltage fault exists when the bq2040 measures a voltage more than 5 above the ChargingVoltage When the bq2040 detects an overvoltage condition the requested charge current is set to 0 and the Terminate_Charge_ Alarm bit is set in BatteryStatus The alarm bit is cleared when the current drops below 256mA and the voltage is less than 105 of ChargingVoltage m Overcurrent An overcurrent fault exists when the bq2040 measures a charge current more than 25 above the ChargingCurrent If the ChargingCurrent is less than 1024mA an overcurrent fault exists if the charge current is more than 1mA above the lowest multiple of 256mA that exceeds the ChargingCurrent When the bq2040 detects an overcurrent condition the requested charge current is set to 0 and the Terminate_Charge_ Alarm bit is set in Battery Status The alarm bit is cleared when the current drops below 256mA a Maximum Temperature When the battery temperature equals the programmed maximum temperature the requested charge current is set to zero and the Over_Temp_Alarm and the Terminate_Charge_Alarm bits are set in Battery Status The Over_Temp_Alarm bit is cleared when the temperature drops to 43 C below the maximum temperature threshold minus 5 C m PSTAT When the PSTAT input is 21 5V the requested charge current is set to 0 and the Terminate_Charge_ Alarm bit is set in BatteryStatus if the Discharging flag is not set The alarm bit is cleared when the PSTAT input is lt 1
52. ymbol Parameter Minimum Typical Maximum Unit Notes Vcc Supply voltage 3 0 4 25 6 5 V a rd me Reference at 25 C 5 7 6 0 6 3 Vs Irer 5uA VREF Reference at 40 C to 85 C 4 5 7 5 V TreF 5A RREF Reference input impedance 2 0 5 0 MQ Vrer 3V 90 135 uA Vcc 3 0V Icc Normal operation 120 180 uA Voc 4 25V 170 250 uA Voc 5 5V Vsp Battery input 0 Vee V RSBmax SB input impedance 10 MQ 0 lt Vsp lt Vcc IpIsP DISP input leakage 5 uA Vpisp Vss Itvout Vout output leakage 0 2 0 2 uA EEPROM off VsR Sense resistor input 0 3 2 0 V by la ee RSR SR input impedance 10 MQ 200mV lt Vsr lt Vcc 0 5 Vec Vec V ESCL ESDA VIH Logic input high 1 4 5 5 V SMBC SMBD Va Loniedhpatios 0 0 3 Voc V ESCL ESDA 0 5 0 6 V SMBC SMBD VoL Data clock output low 0 4 V IoLr 3504 A SMBC SMBD IoL Sink current 100 350 uA VoL lt 0 4V SMBC SMBD VOLSL LEDx output low low Vcc 0 1 V o lt 1 75mA VoLSH LEDx output low high Vcc 0 4 V A lt 11 0mA VoHVL Vout output low Vcc Vcc 0 3 V Vcc 8V Ivout 5 25mA Vouvu Vout output high Voc Voc 0 6 V_ Voc 6 5V Ivout 33 0mA Ivout Vout source current 33 mA At Vonvu Vcc 0 6V Ios LEDx sink current 11 0 mA At Vors 0 4V Note All voltages relative to Vss 28 AC Specifications bq2040 Symbol Parameter Min Max Units Notes Fsmp SMBus operating frequency 10 100 KHz TRUR o e
53. yte Values Notes Reserved Ox2f 00 0 Not currently used by the bq2040 Li Ion taper 0x38 0x39 10 ff 240mA Sets the upper taper limit for Li Ion charge termina current tion Stored in 2 s complement Maximum Sets the maximum amount of overcharge before a overcharge Ox8a Ox3b 9c ff 100mAh maximum overcharge charge suspend occurs limit Stored in 2 s complement Reserved 0x3c 00 0 Must be programmed to 0 Tf the bq2040 is reset and bit 3 of this location is 0 the bq2040 locks access to any command outside of the SBS Access protect 0x3d ba SPD acces only data set Program to 0xb8 for full R W access Oxb0 for SBD access only FLAGS1 Ox38e 00 0 Initializes FLAGS1 Relative display Li Ion chemistry FLAGS2 Ox3f bO bq2040 charge Initializes FLAGS2 control c t The current gain measurement and current integra o tion gain are related and defined for the bq2040 cur measurement 0x46 0x47 00 of 3840 i rent measurement This word equals 192 sense re eae sistor value in ohms Used to adjust the battery voltage offset according to mae voltage 0x48 fe 2mV the following Voltage Vsg mV Vorr Voltage gain The default value zero adjustment for the offset is Temperature 12 8 C or 0x80 offset xaa 8a 13 8 C TOFF New TOFFCURRENT TEMPactuat TEMPREPORTED 10 Maximum oo _ Maximum charge temperature is 69 mt 1 6 C mt temperature Ox4a 5f P upper nibble The AT step is dT 2 16 10 C and AT ste
Download Pdf Manuals
Related Search
Texas lnstruments bq2040 handbook bq4050 technical reference manual