MAXIM MAX6946/MAX6947 Manual
Contents
1. Figure 2 Static and PWM Constant Current Waveforms MAKIM 11 ZV69XVW 9V69XVIN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Ports Configured as Inputs Configure a port as a logic input by writing 0x01 to the port s output register Table 4 Reading an input port register returns the logic levels from the I O ports con figured as a logic input Table 7 The input port regis ter returns logic O in the appropriate bit position for a port not configured as a logic input The input port s registers are read only The MAX6946 MAX6947 ignore a write to input ports register a RST Input The active low RST input operates as a reset that voids any current 12C transaction involving the MAX6946 MAX6947 forcing the devices into the 12C stop condi tion Use the D6 bit in the configuration register to con figure RST to reset all the internal registers to the power on reset state Tables 2 and 3 The RST input is overvoltage tolerant to 6V The MAX6946 MAX6947 ignore all 12C bus activity while RST remains low The MAX6946 MAX6947 use this fea ture to minimize supply current in power critical applica tions by effectively disconnecting the MAX6946 MAX6947 from the bus during idle periods RST also operates as a bus multiplexer allowing multiple MAX6946 MAX6947s to use the same 12C slave address Drive only one MAX6946 MAX6947 RST input high at any time t2. PIN 1 INDICATOR J H y y Yj 0 07 16 60 31 0 03 TOP VIEW SIDE VIEW BOTTOM VIEW JJ Cross section 0 64 0 05 RASS DOI L Q E D DEPOPULATED pke cope min max MIN MAX BUMPS 0 24 0 03 W162B2 1 1 98 211 1 98 2 11 NONE NOTES 1 Terminal pitch is defined by terminal center to center value 2 Outer dimension is defined by center lines between scribe lines 3 All dimensions in millimeters 4 Marking shown is for package orientation reference only 5 6 MAXI PACKAGE OUTLINE 16L WLP PKG 0 5mm PITCH APPROVAL DOCUMENT CONTROL NO 21 0200 Tolerance is 0 02mm unless specified otherwise All dimensions apply to PbFree package codes only REV BIA DRAWING NOT TO SCALE MAKIM 23 ZV69XVW 9V69XVIN 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Revision History REVISION REVISION PAGES NUMBER DATE DESCRIPTION CHANGED 1 7 11 17 19 Added MAX6946C WLP package to the data sheet 1 6 20 23 MAX6946 MAX6947 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product No circuit patent licenses are implied Maxim reserves the right to change the circuitry and specifications without notice at any time 24 Maxim Integrated Products 120 San Gabriel Drive Sunnyvale CA 94086 408 737 7600
3. Note 7 Guaranteed by design Input filters on the SDA and SCL inputs suppress noise spikes of less than 50ns 4 dl A Slab 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Typical Operating Characteristics Ta 25 C unless otherwise noted STANDBY CURRENT Istsy SUPPLY CURRENT lpp STANDBY CURRENT est vs TEMPERATURE vs TEMPERATURE vs TEMPERATURE 2 0 5 25 2 25 3 Vpp 3 6V S S Vpp 3 3V eo Zi 3 20 S 20 S K e 12 5 45 15 3 5 3 gt gt E 0 8 gt 10 A 10 Z SS Z E B E 0 4 5 5 Von 2 7V Von 2 25V 0 0 0 40 25 10 5 20 35 50 65 80 95 110 125 40 25 10 5 20 35 50 65 80 95 110 125 40 25 10 5 20 35 50 65 80 95 110 125 TEMPERATURE C TEMPERATURE C TEMPERATURE C DELTA SUPPLY CURRENT Ipp20 DELTA SUPPLY CURRENT Ipp20 OUTPUT SINKING CURRENT vs TEMPERATURE vs TEMPERATURE vs Vext Vuen AT 10mA 40 15 8 14 g 2 Vpp 3 6V 5 A eg a 12 3 z 36 2 g 12 Von 3 3V 2 E E 10 Z Z E 32 E 9 S 8 i E gt gt S BS E S 2 8 S 6 5 5 z z 4 ZS 24 a 3 Von 2 7V gt Vpp 2 25V 2 0 0 0 40 25 10 5 20 35 50 65 80
4. 2008 Maxim Integrated Products MAXIM is a registered trademark of Maxim Integrated Products Inc
5. is 7 5mA ha is 10mA hal f current curren is 3 75mA s 5mA i curren is 12 5mA h alf curre is 6 25MA curren is 15mA hal curren s 7 5mA Full curren Fi Fi Fi Fi Fi Fi i n i n x lt x lt x lt Xx gt lt gt lt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt lt gt lt gt lt gt lt gt lt gt lt gt lt lt U U U U U U U U current is 17 5mA half current is 8 75mA Full current is 20mA half current is 10mA Table 6 Output Current Register Format ADDRESS x lt lt Xx D Ka lt gt lt Xx alalolo AalaAalolo REGISTER BIT DESCRIPTION CODE HEX e Ed e a e A g o D N ant current ant curren is set to half con ant current ant curren ant current ant curren ant current curren ant current ant curren ant current ant curren ant current curren e ant current ant curren ant current lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt o x Xx Xx Xx eee ant Curren ant current 10 O X gt lt gt lt gt lt XXIX gt lt gt lt gt lt amp lt gt lt LK gt lt 4 o KL gt lt
6. put registers set to value 0x00 or 0x01 are unaffected Table 4 This means that any ports used for GPIOs are still fully operational in shutdown mode and port inputs can be read and output ports can be toggled at any time using the serial interface Use the MAX6946 MAX6947 for a mix of logic inputs logic outputs and PWM LED drivers and only the LED drivers turn off automatically in shutdown Put the MAX6946 MAX6947 into shutdown mode by clearing the run bit bit DO in the configuration register 0x10 Table 2 Exit shutdown by setting the run bit high through the serial interface or by using the Reset Run option see the Reset Run Option section Configure and control the MAX6946 MAX6947 normally through the serial interface in shutdown mode All registers are accessible in shutdown mode and shutdown mode does not change any register values Changing a port from static logic low 0x00 or static logic high 0x01 to a constant current value Ox02 OxFE in shutdown mode turns that output off logic high or high impedance like any other constant current outputs in shutdown The new constant current output starts just like any other constant current outputs when exiting shutdown Changing a port from a constant current value Ox02 OxFE to static logic low 0x00 or static logic high 0x01 in shutdown causes that output to set to the value as a GPIO output The new GPIO output is unaf fected just like any other GPIO output w
7. TA 25 C PWM Disabled All Ports High IstBY fSCL OHz other digital TA TMIN to 85 C Impedance inputs at VDD or GND Ta T Power On Reset Voltage Hysteresis PORHYS N to TMAX Standby Current in Reset RST at GND fscL TA 25 C PWM Disabled All Ports High IRST 400kHz other digital TA 1 to 85 C Impedance inputs at VDD or GND to TMAX Supply Current Interface Active 25 C Reset Run Enabled PWM on ne Wee Disabled All Ports High SR Impedance GND to TMAX One port set to 10mA Ta 25 C constant current all other ports output registers set to 0x00 0x01 or OxFF digital inputs at VDD or GND MIN to TMAX TMIN to 85 C Delta Supply Current Interface Idle One port set to 20mA Ta 25 C constant current all other ports output registers set to 0x00 0x01 or OxFF digital inputs at VDD or D GND MIN to TMAX TMIN to 85 C 2 MAXIN 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control ELECTRICAL CHARACTERISTICS continued VDD 2 25V to 3 6V Ta TMIN to Tmax unless otherwise noted Typical values are at VDD 3 3V TA 25 C Note 1 PARAMETER SYMBOL CONDITIONS TYP MAX UNITS nput High Voltage PO P9 SDA SCL RST ADO OSC PO P9 output register set to 0x01 nput Low Voltage PO P9 SDA SCL RST ADO OSC PO P9 output register set to 0x01 nput Leakage
8. 08 IN PHASE PWM PERIOD gt lt OUTPUT P1 09 STAGGERED PWM PERIOD lt OUTPUT P1 09 STAGGERED PWM PERIOD lt OUTPUT P1 09 STAGGERED PWM PERIOD lt t OUTPUT P2 STAGGERED PWM PERIOD gt lt lt OUTPUT P3 STAGGERED PWM PERIOD gt lt bg t OUTPUT P5 STAGGERED PWM PERIOD gt lt OUTPUT P6 STAGGERED PWM PERIOD lt OUTPUT P7 STAGGERED PWM PERIOD gt lt a OUTPUT P4 STAGGERED PWM PERIOD Figure 3 Staggered PWM Waveform Table 7 Input Ports Registers ADDRESS OUTPUT P2 STAGGERED PWM PERIOD OUTPUT P3 STAGGERED PWM PERIOD bel fg OUTPUT P4 STAGGERED PWM PERIOD gt OUTPUT P5 STAGGERED PWM PERIOD gt lt lt OUTPUT P6 STAGGERED PWM PERIOD gt lt OUTPUT P7 STAGGERED PWM PERIOD gt REGISTER BIT DESCRIPTION CODE HEX Input ports P7 PO Port P7 Port P6 Port P5 oa D3 Port P4 Port P3 Port P2 Port P1 Port PO Input ports P9 and P8 12 Port P9 Port P8 MAKLM 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Shutdown Mode In shutdown mode all ports configured as constant current outputs output register set to a value between 0x02 and OxFE are switched off and these outputs go high impedance as if their registers were set to value OxFF Ports configured as logic inputs or outputs out
9. 95 110 125 40 25 10 5 20 35 50 65 80 95 110125 0 2 3 4 5 TEMPERATURE C TEMPERATURE C Vext Wen V OUTPUT SINKING CURRENT STAGGER PWM PORT WAVEFORMS vs Ver Ven AT 20mA OUTPUT REGISTERS SET TO 0x80 24 OG MAX6946 47 toc08 20 E PORT PO 16 2V div oc es S 1 PORT P4 z 2V div 8 es 5 PORT P7 4 2V div 0 0 1 2 3 4 5 1ms div Vext Wen V dl d Slab 5 ZV69XVW 9V69XVIN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control MAX6946 MAX6947 MAX6946C Pin Description FUNCTION I O Ports Configure PO P4 as open drain current sink outputs rated at 20mA max as CMOS logic inputs or as open drain logic outputs Connect loads to a supply voltage no higher than 7V Ground I O Ports Configure P5 P9 as open drain current sink outputs rated at 20mA max as CMOS logic inputs or as open drain logic outputs Connect loads to a supply voltage no higher than 7V OSC MAX6946 External Oscillator Input ADO MAX6947 Address Input Sets the device slave address see Table 10 Active Low Reset Input Positive Supply Voltage Bypass VDD to GND with a 0 1uF ceramic capacitor CURRENT REFERENCE 2C Compatible Serial Clock Input 2C Compatible Serial Data I O Exposed Pad on Package Underside Connect to GND Do not use as the main ground connection Block Diagram RAM
10. Current P0 P9 SDA SCL RST ADO OSC NH He nput Capacitance PO P9 SDA SCL RST ADO OSC Ta 25 C Output register set to 0x02 TA TMIN to 85 C Vpp 3 3V 16 pin TQFN Ver VLED 1V Note 3 Ta Tmin to 85 C 16 bump WLP 10mA Port Nominal Sink Constant Current PO P9 Ta 25 C Output register set to 0x02 Ta Tmin to 85 C Current PO P9 VDD 3 3V 16 pin TQFN 20mA Port Nominal Sink Constant VEXT VLED 1V Note 3 ae Nore s Ta TMIN to 85 C 16 bump WLP Ta 25 C Vpp 3 3V Vpo to Vpg 1 4V Port Sink Constant Current T 20mA atching 25 C Vpp 3 3V Vpo to VPo 1 4V T 10mMA Port Logic Output Low Voltage put register set to 0x00 PO P9 ISINK 0 5mA Port Logic Output Low put register set to Ox00 Short Circuit Current PO P9 Lp_ 5V Port Slew Time m 20 current to 80 current Output Low Voltage SDA K 6mA MAKINI 3 ZV69XVW 9V6E9XVIN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control TIMING CHARACTERISTICS Figure 8 VDD 2 25V to 3 6V Ta TMIN to Tmax unless otherwise noted Typical values are at VDD 3 3V TA 25 C Note 1 PARAMETER SYMBOL CONDITIONS 16 pin TQFN 16 bump WLP Internal PWM Clock Frequency External PWM Clock Frequency Serial Clock Frequency Bus Free
11. Time Between a STOP and a START Condition Hold Time Repeated START Condition Repeated START Condition Setup Time STOP Condition Setup Time SU STO Data Hold Time tHD DAT Data Setup Time SU DAT SCL Clock Low Period SCL Clock High Period Rise Time of Both SDA and SCL Signals Receiving Fall Time of Both SDA and SCL Signals Receiving Fall Time of SDA Transmitting Pulse Width of Spike Supressed SE Load for Each Bus Line RST Pulse Width RST Rising Edge to Reset Run enabled 16 pin TQFN MAX6946 MAX6947 ACK to Cancel tRSTRUN internal oscillator Reset Run enabled 16 bump WLP RST Rising Edge to MAX6946 MAX6947 ACK to Ensure tRSTRUN Reset Run Reset Run enabled internal oscillator enabled Note 1 All parameters are tested at TA 25 C Specifications over temperature are guaranteed by design Note 2 Port current is factory trimmed to meet a median sink current of 2OmA and 10mA over all ports The AlouT specification guarantees current matching between parts Note 3 A master device must provide a hold time of at least 300ns for the SDA signal referred to V L of the SCL signal in order to bridge the undefined region of SCL s falling edge Note 4 Not production tested Guaranteed by design Note 5 Cp total capacitance of one bus line in picoFarads tR and tF are measured between 0 3 x Vpp and 0 7 x VDD Note 6 Lok lt 6mA
12. by no 12C interface activity to the MAX6946 MAX6947 for 128 to 129 periods of the PWM clock to trigger the Reset MAKIM X lt gt lt lt lt gt lt gt lt gt X lt gt lt x lt lt gt lt gt lt gt lt gt lt gt lt lt gt lt gt lt gt lt gt lt gt lt gt lt P lt x lt lt gt lt gt lt gt lt gt lt gt lt P gt lt x lt lt gt lt gt lt gt lt gt lt gt lt afalajalololo CURRENT 20mA FULL 7 8 6 8 5 8 CURRENT CURRENT CURRENT CURRENT lt RAMP UP 4 8 3 8 2 8 1 8 Tam CURRENT CURRENT CURRENT CURRENT CURRENT RAMP DOWN gt Figure 7 Global Current Modifies Fade Behavior Run option If this timeout period elapses without the MAX6946 MAX6947 acknowledging an 12C transaction the run bit DO in the configuration register sets bring ing the driver out of shutdown and activating any pro grammed ramp up If RST pulses high for less than this timeout period to trigger a Reset Run the MAX6946 MAX6947 ignore the pulse and the MAX6946 MAX6947 continue to wait for a suitable trigger Cancel the Reset Run trigger by transmitting an 12C communication to the MAX6946 MAX6947 before the timeout period elapses The trigger cancels when the MAX6946 MAX6947 acknowledge the 12C transaction 15 ZV69XVW 9V6E9XVIN MAX6946 MAX6947 10 Port Constant
13. Current LED Driver and I O Expander with PWM Intensity Control and requires sending at least the MAX6946 MAX6947s IC slave address When using the internal oscillator the minimum timeout period is 127 45000 equal to 2 822ms When using an external oscillator for the PWM clock the timeout period is 127 OSC The shortest time period allowed is 1 27ms this number corresponds to the maximum OSC frequency of 100kHz When using the internal oscillator the minimum 12C clock speed that guarantees a successful start bit and eight data bits 9 bits total within the minimum timeout period is 9 5 66ms equal to 1590Hz Canceling the Reset Run trigger clears the Reset Run bit D1 in the configura tion register disabling Reset Run The run bit DO in the configuration register remains cleared so the driver remains in shutdown OSC Input The MAX6946 can use an external clock of up to 100kHz instead of the internal 32kHz oscillator Connect the external clock to the OSC input and set the OSC bit in the configuration register to enable the MAX6946 to use the external clock Table 2 Serial Interface Serial Addressing The MAX6946 MAX6947 operate as a slave that sends and receives data through an 2C compatible 2 wire interface The interface uses a serial data line SDA and a serial clock line SCL to achieve bidirectional communication between master s and slave s A master typically a microcontroller initiates all data transfers t
14. ER 7 8125ms NOMINAL PWM PERIOD the timing shown in Figure 2 All outputs therefore draw load current at the exactly same time for the same PWM setting This means that if for example all out puts are set to 0x80 128 256 duty cycle the current draw would be zero all loads off for half the time and full all loads on for the other half Setting the stagger bit causes the PWM timing of the 10 port outputs to stagger by 32 counts of the 256 count PWM period i e 1 8th distributing the port output switching points across the PWM period Figure 3 Staggering reduces the di dt output switching transient on the supply and also reduces the peak mean current requirement Set or clear the stagger bit during shutdown Changing the stagger bit during normal operation can cause a transient flicker in any PWM controlled LEDs because of the fundamental PWM timing changes VALUE i LOW 3 256 DUTY CONSTAI LOW 4 256 DUTY CONSTA e LOW 252 256 DUTY CONS LOW 253 256 DUTY CONSTANT C LOW 254 256 DUTY CONSTANT C UTPUT STATIC HIGH IMPEDA OUTPUT STATIC LOW LOGIC DRIVE WITH INPUT BUFFER ENABLED GPI OUTPUT STATIC HIGH LOGIC DRIVE WITH INPUT BUFFER ENABLED GPI UTPUT STATIC LOW CONSTANT CURRENT WITH INPUT BU LU ATIC LED DRIVE UFFER DISABLED STATIC LED DRIVE
15. P UP RAMP DOWN CONTROLS INTERNAL OSCILLATOR PWM CONTROLLER 1 0 PORTS EXTERNAL CLOCK INPUT MAXIM MAX6946 CONFIGURA SES REGISTE iN 0 REGISTER MAX6946 ONLY 2 WIRE SERIAL INTERFACE MAX6947 ONLY dl A Slab 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Detailed Description The MAX6946 MAX6947 general purpose input output GPIO peripherals provide 10 I O ports PO to P9 con trolled through an 2C compatible serial interface Use the 10 I O ports as logic inputs open drain logic out puts or constant current sinks in any combination Ports withstand 7V independent of the MAX6946 MAX6947s supply voltage whether used as logic inputs logic outputs or constant current sinks The MAX6946 MAX6947 feature shutdown and standby modes for low power dissipation The I O ports feature pulse width modulation PWM of the outputs and can stagger the PWM timing of the 10 port outputs in con secutively phased 45 increments The I O ports also feature ramp up and ramp down controls The MAX6946 MAX6947 feature a RST input to halt any serial interface transmission and bring the device out of shutdown Open drain logic outputs require external pullup resis tors to provide the logic high reference Ports config ured as open drain logic outputs have a relatively weak sink capability but are still adequate for normal logic l
16. TER A SDA BY __ RECEIVER S Figure 11 Acknowledge secutive bytes from the MAX6946 MAX6947 with the first data byte being read from the register addressed by the initialized command byte Figure 14 When per forming read after write verification remember to reset the command byte s address because the stored com mand byte address has been autoincremented after the write Table 1 17 ZV69XVW 9P6E9XVIN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION ACKNOWLEDGE FROM MAX6946 MAX6947 4 i i T e D15 D14 D11 D10 T T T T SLAVE ADDRESS Figure 12 Command Byte Received ACKNOWLEDGE FROM MAX6946 MAX6947 TT MAND BYTE ACKNOWLEDGE FROM MAX6946 MAX6947 ACKNOWLEDGE FROM MAX6946 MAX6947 HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6946 MAX6947s REGISTERS ACKNOWLEDGE FROM MAX6946 MAX6947 HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6946 MAX6947s REGISTERS ACKNOWLEDGE FROM MAX6946 MAX6947 SLAVE ADDRESS 0 COMMAND BYTE DATA BYTE Jale _ N AUTOINCREMENT MEMORY ADDRESS Figure 14 n Data Bytes Received Operation with Multiple Masters If the MAX6946 MAX6947 operates on a 2 wire inter face with multiple masters a master reading the MAX6946 MAX6947 should use a repeated start between the write This sets the MAX6946 MAX6947 address pointer a
17. ast DJs I bs NOTES 1 DIMENSIONING amp TOLERANCING CONFORM TO ASME Y14 5M 1994 2 ALL DIMENSIONS ARE IN MILLIMETERS ANGLES ARE IN DEGREES 3 IS THE TOTAL NUMBER OF TERMINALS HE TERMINAL 1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95 1 SPP 012 DETAILS OF TERMINAL 1 IDENTIFIER ARE OPTIONAL BUT MUST BE LOCATED WITHIN THE ZONE INDICATED THE TERMINAL 1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0 20 mm AND 0 25 mm FROM TERMINAL TIP Te DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION d n COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS 9 DRAWING CONFORMS TO JEDEC MO220 REVISION C Z MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY HDALLAS SA AXLYVI 11 NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY SEMICONDUCTOR 12 WARPAGE NOT TO EXCEED 0 10mm A ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY ME PACKAGE OUTLINE 8 12 16L THIN QFN 3x3x0 8mm DOCUMENT CONTROL NO 2 DRAWING NOT TO SCALE re 21 0136 wi 22 MAXIA 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Package Information continued The package drawing s in this data sheet may not reflect the most current specifications For the latest package outline information go to www maxim ic com packages E sl 1 0 025 BSC
18. ction The I O ports are high impedance without Vpp applied and remain high impedance upon power up Figure 1 shows the I O port structure of the MAX6946 MAX6947 I O ports PO to P9 default to high impedance on power up so LEDs or other port loads connected draw no current Ports used as inputs do not load their source signals 1 0 PORT POSITION A 0x00 0x01 POSITION B 0x02 OxFF CLOSE SWITCH 0x02 0xFE LATC TPO PWM STER GENERATOR LATC TO FROM CURRENT SERIAL STER INTERFACE 3 BIT LATCH GLOBAL CURRENT REGISTER READ 1 0 4 BIT DAC 0x00 ENABLE PORT COMMAND Figure 1 Simplified Schematic of I O Ports Table 4 Individual Port Configuration Options Port Output Registers 0x00 0x09 OUTPUT REGISTER CODE PORT TYPE REGISTER BIT DO 1 Low logic output RUN MODE CONFIGURATION SHUTDOWN CONFIGURATION REGISTER BIT DO 0 APPLICATION NOTES Logic low output not constant current High logic output Logic input Logic high output with external pullup resistor otherwise high impedance CMOS logic input Lowest supply current unaffected by shutdown Constant current static sink output Static constant current sink output Full constant current drive with no PWM Constant current PWM output 0x03 3 256 PWM duty cycle OxFE 254 256 PWM duty cycle 0x03 0xFE High impedance Adjustable consta
19. ee ON KIT VALUATI E AW AILABLE 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control General Description Features The MAX6946 MAX6947 2C SMBus compatible 2 25V to 3 6V Operation serial interfaced peripherals provide microprocessors I O Ports Default to High Impedance LEDs Off with 10 I O ports rated to 7V on Power Up Each port can be configured as a 2 5mA to 20mA con I O Port Inputs Are Overvoltage Protected to 7V stant current LED driver static or PWM a 1 25mA to I O Port Outputs Are 7V Rated Open Drain 10mA 10mA constant current LED driver static or PWM an or 20mA Constant Current Static PWM LED open drain logic output or an overvoltage protected Drivers or Open Drain Logic Outputs Schmitt logic input I O Ports Support Hot Insertion Analog and switching LED intensity control includes indi Individual 8 Bit PWM Intensity Control for Each LED vidual 8 bit PWM control per output individual 1 bit ana RST Input Clears Serial Interface and Can Exit log current control half full scale per output and a global Shutdown Warm Start 3 bit DAC current control that applies to all LED outputs MAX6946 OSC Input Allows for External PWM The MAX6946 MAX6947 can stagger the PWM timing of Clock Input the 10 port outputs in consecutively phased 45 incre MAX6947 ADO Input Selects from Two Slave ments Staggering the outputs spreads the PWM load Addresses currents over time i
20. evel outputs The weak drive means that the short cir cuit current is low enough that inadvertently driving an LED from a port configured as a logic output is unlikely to damage the LED The MAX6946 features a fixed 12C slave address of 010 0000 and provides an OSC input to accept an external PWM clock input as an alternative to the inter nal PWM clock The MAX6947 features an ADO input that uses two level logic to select from two 12C slave addresses The MAX6947 always uses the internal PWM clock Register Structure The MAX6946 MAX6947 contain 22 internal registers see Table 1 Use registers 0x00 to 0x09 to individually control ports PO to P9 Registers Ox0A to Ox0D allow more than one port control register to be written with the same data to simplify software Registers OxOE and OxOF do not store data but return the port input status when read Registers 0x10 to 0x15 configure and con trol the device operation MAKINI Table 1 Register Address Map DESCRIPTION ADDRESS CODE HEX AUTO INCREMENT ADDRESS PO outp or PW 0x00 0x01 P1 outp or PW P2 outp 0x01 0x02 P3 outp P4 outp P5 outp P6 outp P7 outp P8 outp P9 outpu or PW ite ports PO P9 with same put level or PWM Read port PO output level or PWM Write ports PO P3 with same put level or PWM evel or PWM ite ports P4 P7 with same put level or PWM Read port P4 outp
21. for a given capacitive load en vs Vuen SUPPLY 25 30 35 40 45 50 55 60 65 7 0 Ven SUPP 19 ZV69XVW 9V6E9XVN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Using Stagger with Fewer Ports The stagger option when selected applies to all ports configured as constant current outputs The 10 ports PWM cycles are separated to eight evenly spaced start positions Figure 3 Optimize phasing when using fewer than 10 ports as constant current outputs by allo cating the ports with the most appropriate start posi tions If using eight constant current outputs choose PO P7 because these all have different PWM start posi tions If using four constant current outputs choose PO P2 P4 P6 or P1 P3 P5 P7 because their PWM start positions are evenly spaced In general choose the ports that spread the PWM start positions as evenly as possible This optimally spreads out the current demand from the ports load supply Generating a Shutdown Run Output The MAX6946 MAX6947 can use an I O port to auto matically generate a shutdown run output The shut down run output is active low when the MAX6946 MAX6947 are in run mode hold off fade off or ramp up and goes high automatically when the devices final ly enter shutdown after fade off Programming the port s output register to value 0x02 puts the output into static constan
22. hen exiting shutdown Ramp Up and Ramp Down Controls The MAX6946 MAX6947 provide controls that allow the output currents to ramp down into shutdown ramp down and ramp up again out of shutdown ramp up Figures 4 and 5 Ramp down comprises a programma ble hold off delay that also maintains the outputs at full current for a time before the programmed fade off time After the hold off delay the output currents ramp down FULL CURRENT HALF CURRENT Figure 4 Ramp Up Behavior ERO TO 4s HOLD OFF DELAY BEFORE FADE OFF ZERO TO 8s CURRENT RAMP DOWN i ZERO TO 4s CURRENT FADE OFF AFTER HOLD OFF DELAY Y FULL CURRENT HALF CURRENT 0 s 11 4s 1 2s 1s 2s 4s d 1 2s 1s IL 1 8s AIL ings Figure 5 Ramp Down Hold Off and Fade Off Behavior MAKIM II IL 1 85 1 uge 13 ZV69XVW 9V6E9XVIN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control CURRENT PORT CURRENT FULL DE 17 5mA 4 15mA 4 PORT CURRENT HALF FULL ra FADE UP 2 8 1 ZERO CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT FADE OFF gt Figure 6 Output Fade DAC Global Current 0x07 Table 8 Ramp Down Register Format 0X11 DESCRIPTION Instant going into shutdown after hold off delay The ramp down register sets the hold off and fade off times and all
23. ion by transitioning SDA from low to high while SCL is high The bus is then free for another transmission Figure 9 Bit Transfer One data bit is transferred during each clock pulse The data on SDA must remain stable while SCL is high Figure 10 Acknowledge Any bytes received after the command byte are data bytes The first data byte goes into the internal register of the MAX6946 MAX6947 selected by the command byte Figure 11 If multiple data bytes are transmitted before a STOP condition is detected these bytes are generally stored in subsequent MAX6946 MAX6947 internal registers because the command byte autoin crements Table 1 Message Format for Reading Read from the MAX6946 MAX6947 using the MAX6946 MAX6947s internally stored command byte as an address pointer the same way the stored com mand byte is used as an address pointer for a write The pointer autoincrements after each data byte is read using the same rules as for a write Table 1 Thus a read is initiated by first configuring the MAX6946 MAX6947s command byte by performing a write Figures 12 and 13 The master can now read n con MAKIM oe US Ag ASAT START STOP CONDITION CONDITION Figure 9 Start and Stop Conditions DATA LINE STABLE CHANGE OF DATA DATA VALID ALLOWED Figure 10 Bit Transfer CLOCK PULSE START CONDITION FOR ACKNOWLEDGE aT _JT _ _ AS E EE SDA BY TRANSMIT
24. ith a 0 1uF ceramic capacitor as close as possi ble to the device Chip Information PROCESS BiCMOS Pin Configurations continued TOP VIEW MAXIM MAX6946 MAX6947 TQFN 3mm x 3mm MAX6947 ONLY dl A Slab 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Package Information The package drawing s in this data sheet may not reflect the most current specifications For the latest package outline information go to www maxim ic com packages MARKING 12x16L QFN THIN EPS ZV69XVW 9V6E9XVIN AX INDEX AREA D 2 X E 2 BOTTOM VIEW 70 10 C R IS OPTIONAL DAL gt eee PRALLAS VLAXIL VI TIME SDE vew DRAWING NOT TO SCALE M T AS Ma MAKIM 21 MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Package Information continued The package drawing s in this data sheet may not reflect the most current specifications For the latest package outline information go to www maxim ic com packages EXPOSED PAD VARIATIONS ew ow e _A_ 0 70 0 75 0 80 0 75 a Nom Jax min Nom max 025 oso tass3 1 0 25 ozo 125 025 o70 1 25 035x45 weec o 220 300 3 10 220 3 00 310 290 3 00 3 10 a EE 2 90 3 00 3 10 290 3 00 3 10 290 3 00 3 10 e 235 ven EN H aE Dee e s os o a a 0 oor Joos o oo oo o ove 005 0 85 P 0 20 REF Dez Loes Los is C
25. lt gt lt gt lt gt lt gt lt gt lt lt gt lt gt gt lt gt lt gt lt gt lt gt lt gt lt gt lt 1 gt gt lt 4 O gt lt gt lt gt K gt lt gt lt P lt i it lt gt lt gt lt gt lt gt lt gt lt 4 O gt lt XXIX gt lt gt lt gt lt gt lt K gt lt gt lt gt lt x x x MAAKLM 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control PWM Intensity Control and Phasing The MAX6946 MAX6947 use an internal 32kHz oscilla tor to generate PWM timing for LED intensity control The MAX6946 also features an OSC input to allow for an external clock for generating PWM timing for LED intensity control Select the PWM clock source for the MAX6946 with configuration register bit D7 Table 2 The MAX6947 powers up configured to use the internal 32kHz oscillator by default The MAX6946 powers up configured to use the external clock source by default A PWM period comprises 256 cycles of the nominal 32kHz PWM clock Figure 2 Individually set the ports PWM duty cycle between 3 256 and 254 256 See Table 4 for port register settings Configure PWM timing by setting the stagger bit in the configuration register Table 2 either with output stag gering or without Clearing the stagger bit causes all outputs using PWM to switch at the same time using OUTPUT REGIST
26. n eight steps helping to even out Auto Ramp Up Out of Shutdown and Up to 4s the power supply current and reduce the RMS current Hold Off Before Ramp Down into Shutdown For a similar part with an SPI QSPI or MICROWIRE 0 8pA typ Shutdown Current compatible interface refer to the MAX6966 MAX6967 40 C to 125 C Temperature Range data sheet a Tiny WLP Package 4 x 4 Grid Applications Ordering Information Cellular Phones LCD Backlights Portable Equipment Keypad Backlights PIN PACKAGE RGB LED Drivers LED Status Indicators MAX6946ATE 7 E T1633 4 MAX6946CAWE W162B2 1 MAX6947ATE E T1633 4 Denotes a lead free package EP Exposed pad Note All devices are specified over the 40 C to 125 C operating temperature range Typical Operating Circuit Ver 5V SC MAXIMI Pin Configurations MAX6946 MAX6947 TOP VIEW MAXIM _ MAX6946C i GIC INPU MAX6946 ONLY MAX6947 ONLY SMBus is a trademark of Intel Corp SPI and QSPI are trademarks of Motorola Inc MICROWIRE is a trademark of National Semiconductor Corp BUMPS ON BOTTOM 16 BUMP 2 1mm x 2 1mm WLP Pin Configurations continued at end of data sheet MAXKLMNI Maxim Integrated Products 1 For pricing delivery and ordering information please contact Maxim Direct at 1 888 629 4642 or visit Maxim s website at www maxim ic com ZV69XVW 9PE9XVIN MAX6946 MAX6947 10 Por
27. n ramp up Device in ramp up Reset Run disabled RST RUN enable Shutdow Reset Run enabled n mode RUN enable Run mode The OSCEN bit applies only to the MAX6946 OSCEN is always 0 for the MAX6947 and the MAX6947 ignores writes to the OSCEN bit Read only bits Table 3 Initial Power Up Register Status DESCRIPTION Port PO P9 output level or PWM POWER UP CONDITION Port 0 9 high impedance ADDRESS REGISTER BIT CODE HEX D7 D4 D3 0x00 0x09 1 1 1 Configuration Shutdown mode Reset Run disabled 0x10 Ramp down hold off Fade hold off disabled Ramp up Disabled 0x11 0x12 Output current ISE 70 IPEAK 10mA for ports P7 PO 0x13 Output current IS Global current 98 IPEAK 10mA for ports P9 P8 Full current Value is O for MAX6947 and 1 for MAX6946 bit 0x14 0x15 MAAKLM 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control LO Ports The MAX6946 MAX6947 contain 10 I O ports Configure the 10 I O ports as logic inputs open drain logic outputs or constant current sinks in any combina tion Table 4 shows a detailed description of the indi vidual port configuration registers 0x00 through 0x09 Use registers 0x00 0x09 to individually assign each port as a logic input open drain logic output or con stant current sink see the PWM Intensity Control and Phasing se
28. nario the LED supply falls significantly below the brownout point when the battery is at end of life voltage 3V Figure 15 shows the typical current sink by a LITEON LTST C170TBKT 3 0V blue LED as the LED supply volt age is varied from 2 5V to 7V The LED currents shown are for ports programmed for 10mA and 20mA constant current swept over a 2 5V to 7V LED supply voltage range It can be seen that the LED forward voltage falls with current allowing the LED current to fall gracefully not abruptly in brownout In practice the LED current drops to 6mA to 7mA at a 3V LED supply voltage this is acceptable performance at end of life in many back light applications Output Level Translation The open drain output architecture allows the ports to level translate the outputs to higher or lower voltages than the MAX6946 MAX6947 supply Use an external pullup resistor on any output to convert the high imped ance logic high condition to a positive voltage level Connect the resistor to any voltage up to 7V When using a pullup on a constant current output select the resistor value to sink no more than a few hundred micramps in logic low condition This ensures that the current sink output saturates close to GND For inter facing CMOS inputs a pullup resistor value of 220kQ is a good starting point Use a lower resistance to improve noise immunity in applications where power consumption is less critical or where a faster rise time is needed
29. nd the read s that takes the data from the location s Table 1 This is because it is pos sible for master 2 to take over the bus after master 1 has set up the MAX6946 MAX6947s address pointer then master 1 s delayed read can be from an unexpect ed location Command Address Autoincrementing The command address stored in the MAX6946 MAX6947 increments through the grouped register func tions after each data byte is written or read Table 1 18 Applications Information Port Input and 12C Interface Level Translation from Higher or Lower Logic Voltages The MAX6946 MAX6947s 12C interface SDA SCL and IOC slave address select input ADO MAX6947 only PWM clock input OSC MAX6946 only and reset input RST are overvoltage protected to 6V independent of Vpp The 10 I O ports PO P9 are overvoltage protected to 8V independent of Vpp This allows the MAX6946 MAX6947 to operate from one supply voltage such as 3 3V while driving the 12C interface and or some of the 10 I O as inputs from a higher logic level such as 5V MAKII 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control a Hot Insertion The RST SCL and ADO inputs and SDA remain high impedance with up to 6V asserted on them when the MAX6946 MAX6947 power down Vpp OV I O ports PO to P9 remain high impedance with up to 8V asserted on them when the MAX6946 MAX6947 power down Use the MAX6946 MAX6947 in hot swap application
30. nt current LED off high impedance Logic high output with external pullup resistor otherwise LED off MAKIM ZV69XVW 9V69XVIN MAX6946 MAX6947 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Ports Configured as Outputs The global current register sets the full maximum con stant current sink into an I O port configured as an out put Table 5 Each output port s individual constant current sink can set to either half or full scale of the global current by the output current registers Table 6 By default maximum current is 20mA hence the default maximum half current is 10mA Set each output port s individual constant current sink to either half scale or full scale of the global current Use the output current registers to set the individual currents Table 6 Set the global current by the global current register Table 5 Set each output current individually to best suit the maximum operating current of an LED load or even adjust on the fly to double the effective intensity control range of each output The individual current selection is 10mA half or 20mA full when setting the global cur rent register to its maximum value Table 5 Global Current Register Format 0x15 REGISTER BIT DESCRIPTION D7 is 2 5mA ha f current is 1 25mA e Ed e a e Co D N D curren is 5mA half current is 2 5mA curren curren
31. o and from the MAX6946 MAX6947 and gen erates the SCL clock that synchronizes the data trans fer Figure 8 The MAX6946 MAX6947 SDA line operates as both an input and an open drain output A pullup resistor typi cally 4 7kQ is required on SDA The MAX6946 MAX6947 SCL line operates as an input A pullup resis tor typically 4 7kQ is required on SCL if there are mul tiple masters on the 2 wire interface or if the master in a single master system has an open drain SCL output Each transmission consists of a START condition Figure 9 sent by a master followed by the MAX6946 MAX6947 7 bit slave address plus the R W bit a regis ter address byte one or more data bytes and finally a STOP condition Figure 9 SCL Ip zm gt START CONDITION Figure 8 2 Wire Serial Interface Timing Details 16 Ip zm tsu sto A REPEATED START CONDITION STOP START CONDITION CONDITION MAXIA 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Table 10 MAX6946 MAX6947 Slave Addresses MAX6947 ADO GND SLAVE ADDRESS 010 0000 ADO Vop 010 0100 MAX6946 010 0000 Start and Stop Conditions Both SCL and SDA remain high when the interface is not busy A master signals the beginning of a transmis sion with a START S condition by transitioning SDA from high to low while SCL is high When the master fin ishes communicating with the slave it issues a STOP P condit
32. o use RST as a bus multiplexer 7 8125ms NOMINAL PWM PERIOD NEXT PWM PERIOD The MAX6946 MAX6947 feature a Reset Run option so that simply taking the RST input high brings the driver out of shutdown in addition to its normal function of enabling the devices 12C interface Standby Mode and Operating Current Configuring all the ports as logic inputs or outputs all output registers set to value 0x00 or 0x01 or LED off output register set to value OxFF puts the MAX6946 MAX6947 into standby mode Put the MAX6946 MAX6947 into standby mode for lowest supply current consumption Setting a port as a constant current output increases the operating current output register set to a value between 0x02 and OxFE even if a load is not applied to the port The MAX6946 MAX6947 enable an internal current mirror to provide the accurate constant current sink Enabling the internal current mirror increases the devices supply current Each output contains a gated mirror and each mirror is only enabled when required In PWM mode the current mirror is only turned on for the output s on time This means that the operating cur rent varies as constant current outputs are turned on and off through the serial interface as well as by the PWM intensity control NEXT PWM PERIOD 64 96 128 160 192 224 256 lt t OUTPUTS PO 08 IN PHASE PWM PERIOD lt OUTPUTS PO 08 IN PHASE PWM PERIOD lt OUTPUTS PO
33. old off delay before fade off going into shutdown O JO x x x x O JO x x x x lt 1O xX1xX x x lt 0 0 0 0 1 1 1 1 A A A x lt gt lt amp K gt lt 1K gt lt X lt lt x lt lt lt lt Xx ze 1 8s hold off delay before fade off going into shutdown EARS ESESESAEAE A 1 4s hold off delay before fade off going into shutdown 1 2s hold off delay before fade off going into shutdown 1s hold off delay befor e fade off going into shutdown 14 lt lt X xX XP lt P lt p Kx ae yas fp OyOy sty Ast O O lt x lt lt lt lt lt Kx aAlO A O Ay yOy Alo MAKILA 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control Table 9 Ramp Up Register Format 0x12 DESCRIPTION Instant full current coming out from shutdown 1 16s ramp up to full current coming out from shutdown REGISTER BIT EI Ku EI ZS 7 Ka CH 1 8s ramp up to full current coming out from shutdown 1 4s ramp up to full current coming out from shutdown 1 2s ramp up to full current coming out from shutdown 1s ramp up to full current coming out from shutdown 2s ramp up to full current coming out from shutdown 4s ramp up to full current coming out from shutdown Ramp up and ramp down use the PWM clock for tim ing When using the external oscillator make sure the oscillator runs until the end of the sequence The inte
34. ows disabling of hold off and fade off zero delay if desired Table 8 The ramp up register sets the ramp up time and allows disabling of ramp up zero delay if desired Table 9 The configuration register contains three status bits that identify the condition of the MAX6946 MAX6947 hold off fade off or ramp up Table 2 The configuration register also enables or dis ables ramp up One write command to the configuration register can put the MAX6946 MAX6947 into shutdown using hold off and fade off settings in the fade register and one read command to the configuration register can determine whether the Reset Run is enabled for restart and whether the MAX6946 MAX6947 will use ramp up on restart REGISTER BIT D3 D2 1 16s ramp down from full current before shutdown after hold off delay 1 8s ramp down from 1 2s ramp down from ull current before shutdown after hold off delay 1 4s ramp down from full current before shutdown after hold off delay ull current before shutdown after hold off delay lt lt lt lt lt x lt x lt lt lt lt lt lt lt lt lt x lt gt lt gt lt Xx 1s ramp down from fu current before shutdown after hold off delay 2s ramp down from fu 4s ramp down from fu current before shutdown after hold off delay current before shutdown after hold off delay Zero hold off delay be ore fade off going into shutdown 1 16s h
35. r nal oscillator always runs during a fade sequence even if none of the ports use PWM The ramp up and ramp down circuit operates a 3 bit DAC The DAC adjusts the internal current reference used to set the constant current outputs in a similar manner to the global current register Table 5 The MAX6946 MAX6947 scale the master current reference so all output constant current and PWM settings adjust at the same ratio with respect to each other This means the LEDs always fade at the same rate even if with different intensity settings The maximum port output current set by the global cur rent register Table 5 also sets the point during ramp down that the current starts falling and the point during ramp up that the current stops rising Figure 7 shows the ramp waveforms that occur with different global current register settings Reset Run Option The MAX6946 MAX6947 feature a Reset Run option so that simply taking the RST input high brings the driver out of shutdown in addition to its normal function of enabling the MAX6946 MAX6947s DC interface This provides an alternative method of bringing the driver out of shutdown to writing to the configuration register through the serial interface The Reset Run timing uses the PWM clock either the internal nominal 32kHz oscil lator or a user provided clock fed into the OSC input MAX6946 only After enabling the Reset Run option the MAX6946 MAX6947 use the rising edge on RST followed
36. s Differences Between the MAX6946 and MAX6947 The MAX6946 features the OSC input allowing the device to use an external clock as the PWM clock source The MAX6946 features a fixed 12C slave address of 0100000 The MAX6947 features an ADO input allowing two unique 12C addresses Table 10 The MAX6947 always uses the internal 32kHz oscillator as the PWM clock source Driving LEDs into Brownout The MAX6946 MAX6947 correctly regulate the con stant current outputs provided there is a minimum volt age drop across the port output This port output voltage is the difference between the load typically LED supply and the load voltage drop LED forward voltage If the LED supply drops so that the minimum port output voltage is not maintained the driver output stages brownout and the load current falls The mini mum port voltage is approximately 0 5V at 10mA sink current and approximately 1V at 20mA sink current Operating the LEDs directly from a battery supply can cause brownouts For example the LED supply voltage is a single rechargeable lithium ion battery with a maxi mum terminal voltage of 4 2V on charge 3 4V to 3 7V Vuen ve Vuen SUPPLY 3 05 3 00 2 95 2 90 2 85 2 80 275 2 70 2 65 2 60 255 h 2 50 25 30 35 40 45 50 55 60 65 7 0 Ven SUPP Figure 15 LED Brownout MAKIM most of the time and down to 3V when discharged In this sce
37. t Constant Current LED Driver and I O Expander with PWM Intensity Control ABSOLUTE MAXIMUM RATINGS VDD TO GND tagos a a n R 0 3V to 4V Continuous Power Dissipation Ta 70 C SCL SDA ADO RST OSC to GND 0 3V to 6V 16 Pin TQFN derate 14 7mW C over 70 C 1176mW Leben GB EE IER E 0 3V to 8V 16 Bump WLP derate 13 3mW C over 70 C 1066mW DG Currentinto PO to PO osmoni 24mA Operating Temperature Range TMIN TMAX 40 C to 125 C DC Current to GA 10mA JUNCTION Temperature annsin C RST Sink CUTEM onn naie e Ta e iias 10mA Storage Temperature Range s o C Total GND Current nejinak i ei 280mA Lead Temperature soldering 10s C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied Exposure to absolute maximum rating conditions for extended periods may affect device reliability ELECTRICAL CHARACTERISTICS VDD 2 25V to 3 6V TA TMIN to Tmax unless otherwise noted Typical values are at Vpp 3 3V TA 25 C Note 1 PARAMETER SYMBOL CONDITIONS Operating Supply Voltage VDD Output Load External Supply Voltage PO P9 VEXT Power On Reset Voltage Vpor Vpp rising 16 pin TQFN 16 bump WLP Standby Current Interface Idle RST at VDD
38. t current mode Table 4 Program the port s output current register to half current Table 6 to mini mize operating current Connect a 220kQ pullup resis tor to this port In run mode the output port goes low approaching OV as the port s static constant current saturates trying to sink a higher current than the 220kQ pullup resistor can source 20 In shutdown mode the output goes high impedance together with any other constant current outputs This output remains low during ramp up and fade down sequences because the current drawn by the 220kQ pullup resistor is much smaller than the available output constant current even at the lowest fade current step Driving Load Currents Higher than 20mA The MAX6946 MAX6947 can drive loads needing more than 20mA like high current white LEDs by paralleling outputs For example consider a white LED that requires 70mA Drive this LED using the ports PO P3 connected in parallel shorted together Configure three of the ports for full current 20mA and configure the last port for half current 10mA to meet the 70mA requirement Control the four ports simultaneously with one write access using register OxOB Table 1 Note that because the output ports are current limiting they do not need to switch simultaneously to ensure safe current sharing Power Supply Considerations The MAX6946 MAX6947 operate with a power supply voltage of 2 25V to 3 6V Bypass the power supply to GND w
39. ut level or PWM ite ports P8 or P9 with same put level or PWM Read port P8 output level or PWM Read ports P7 P0 inputs Read ports P9 and P8 inputs Configuration Ramp down Ramp up Output current ISET70 Output current ISET98 Global current Factory reserved do not write to this register ZLV69XVW 9V69XVIN 10 Port Constant Current LED Driver and I O Expander with PWM Intensity Control mode Table 2 REGISTER BIT Configuration Register 0x10 Use the configuration register to select PWM phasing between outputs startup from shutdown and select shutdown or run test fade status enable hardware Table 2 Configuration Register 0x10 DESCRIPTION VALUE External Initial Power Up All control registers reset upon power up Table 3 Power up status sets I O ports PO to P9 to high imped ance and puts the device into shutdown The MAX6946 MAX6947 powers up in shutdown FUNCTION 0 nternal oscillator enabled as PWM clock source OSC enable S oscillator input enabled as PWM clock source RST does not change register data RSTPOR options PWM ou RST resets registers to POR power on reset state puts are in phase PWM stagger 99 1 PWM ou puts stagger phase MAX6946 MAX6947 0 Device n Hold off status Device n ot in hold off ot in fade off Fade off status Device in fade off Device n Ramp up status ot i
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MAXIM MAX6946/MAX6947 Manual