MAXIM MAX3238 handbook
Contents
1. unless otherwise noted Typical values are at Ta 25 C PARAMETER CONDITIONS MIN TYP MAX UNITS AutoShutdown FORCEON GND FORCEOFF Vcc Receiver Input Threshold to Figure 7a Positive threshold 2 7 yV INVALID Output High Negative threshold 2 7 Receiver Input Threshold to INVALID Output Low igure 4a 0 3 0 3 V INVALID Output Voltage Low OUT 1 6mA 0 4 V RAET Y _ Voc INVALID Output Voltage High OUT 1 0mA 06 V Receiver Positive or Negative PATB 4 Threshold to INVALID High nyp VCC 5V Figure 4b ms H3 Receiver Positive or Negative 7 Threshold to INVALID Low tiny VCC 5V Figure 4b 99 ps Receiver or Transmitter Edge to Transmitters Enabled twu Vcc 5V Figure 4b Note 2 25 ps Receiver or Transmitter Edge to Figure 4b Note 2 15 30 60 sec Shutdown tAUTOSHDN E TRANSMITTER OUTPUTS Output Voltage Swing All transmitter outputs loaded with 3kQ to ground 5 0 5 4 V Output Resistance Vcc V V GND Tout 2V 300 10M POE Vcc lt 3 6V 35 60 Output Short Circuit Current mA Vcc gt 3 6V 40 100 Vout 12V Vcc OV to 5 5V Output Leakage Current iransinitters disabled 25 HA TIMING CHARACTERISTICS Maximum Data Rate RL 3kQ CL 1000pF one transmitter switching 250 kbps Receiver Propagation Delay P_IN to R OUT IPL us CL 150pF tPLH 0 15 R2. Since ei ilps a on 0 3V to 7V VNOSI Jei Sects aar e ney Mote dies os oth iat See 0 3V to 7V VEIA NOTE Ti cree teased snails etal ote head dete talt ot fects Air oe cotta 13V Input Voltages T_IN FORCEOFF FORCEON PEIN 2 docetiesSessadeatd shaeaaygt E leebasta Stennis teede 25V Output Voltages TEBOW T cities tescensee a E A hata eae 13 2V R OUT INVALID nieren een neh nieces 0 3V to Vcc 0 3V Short Circuit Duration T_OUT one at a time ee ececeeeeeeeeeeeeeteeeteeetens Continuous Continuous Power Dissipation Ta 70 C SSOP derate 9 52mW C above 70 C s 762mMW Operating Temperature Ranges MAX3238CAI 70 C MAX3238EAI 85 C Storage Temperature Range 65 C to 160 C Lead Temperature soldering 10S n 300 C Note 1 V and V can have a maximum magnitude of 7V but their absolute difference can not exceed 13V 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 Vcc 3 0V to 5 5V C1 C4 0 1pF tested at 3 3V 45 C1 C4 0 22uF tested at 3 3V 10 C1 0 047uF and C2 C4 0 33uF tested
3. at 5 0V 10 Ta Tmin to Tmax unless otherwise noted Typical values are at Ta 25 C PARAMETER CONDITIONS MIN TYP MAX UNITS DC CHARACTERISTICS Vcc 3 3V or 5 0V Ta 25 C receivers idle 10 40 Supply Current AutoShutdown Plus transmitters idle FORCEON GND i HA FORCEOFF Vcc aeo 1 0 10 Supply Current Shutdown FORCEOFF GND Ta 25 C yA Supply Current AutoShutdown Plus EORCEON FORCEORE Vcc no load 05 20 mA Disabled LOGIC INPUTS AND RECEIVER OUTPUTS Input Logic Threshold Low T_IN FORCEON FORCEOFF 0 8 V Vcc 3 3V 2 0 Input Logic Threshold High V Vcc 5 0V 2 4 Input Leakage Current T_IN FORCEON FORCEOFF 0 01 1 0 HA Output Leakage Current Receivers disabled 0 05 10 HA Output Voltage Low louT 1 6mA 0 4 V Output Voltage High lout 1 0MA Vcc Vcc V 0 6 0 1 RECEIVER INPUTS Input Voltage Range 25 25 V Vcc 3 3V 0 6 1 2 Input Threshold Low V Vcc 5 0V 0 8 1 5 Vcc 3 3V 1 5 2 4 Input Threshold High V Vcc 5 0V 1 8 2 4 Input Hysteresis 0 3 V Input Resistance Ta 25 C 3 5 7 kQ 2 MAXIM 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus ELECTRICAL CHARACTERISTICS continued Vcc 3 0V to 5 5V C1 C4 0 1pF tested at 3 3V 45 C1 C4 0 22uF tested at 3 3V 10 C1 0 047uF and C2 C4 0 33uF tested at 5 0V 10 Ta Tmin to Tmax
4. increased without changing C1 s value However do not increase C1 without also increasing the values of C2 C3 C4 and CBypass to maintain the proper ratios C1 to the other capacitors MAXIM 30us TIMER INVALID R INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN 0 3V AND 0 3V FOR AT LEAST 30us Figure 3a INVALID Functional Diagram INVALID Low 42 7V Da R_IN oH 4 30us i TIMER 2v j INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN 2 7V AND 2 7V FOR LESS THAN 30us INVALID Figure 3b INVALID Functional Diagram INVALID High EDGE TIN petect FORCEOFF O AUTOSHDN _ EDGE DETECT Figure 3c AutoShutdown Plus Logic FORCEQFF POWERDOWN FORCEON AUTOSHDN POWERDOWN IS ONLY AN INTERNAL SIGNAL IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES Figure 3d Power Down Logic 8ETEXVIN MAX3238 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus When using the minimum required capacitor values make sure the capacitor value does not degrade excessively with temperature If in doubt use capaci tors with a larger nominal value The capacitor s equiv alent series resistance ESR which usually rises at low temperatures influences the amount of ripple on V VALID HIGH a DETERMINATE and V EE z INVALID Low Tabl
5. output which allows external devices such as a modem to be monitored without for ward biasing the protection diodes in circuitry that may have Vcc completely removed The MAX3238 is available in a space saving SSOP package Applications Notebook Subnotebook and Palmtop Computers High Speed Modems Battery Powered Equipment Hand Held Equipment Peripherals Printers Typical Operating Circuit appears at end of data sheet AutoShutdown Plus is a trademark of Maxim Integrated Products MAXIM Features 1A Supply Current Achieved with AutoShutdown Plus Guaranteed Data Rate 250kbps 1pA Low Power Shutdown Receivers Active in AutoShutdown Plus Mode Flow Through Pinout Meets EIA TIA 232 Specifications Down to 3 0V Guaranteed 6V us Slew Rate gt gt gt a o Ordering Information PART TEMP RANGE PIN PACKAGE MAX3238CAI 0 C to 70 C 28 SSOP MAX3238EAI 40 C to 85 C 28 SSOP Pin Configuration TOP VIEW MAXIM MAX3238 FORCEO FORCEOF Maxim Integrated Products 1 For pricing delivery and ordering information please contact Maxim Dallas Direct at 1 888 629 4642 or visit Maxim s website at www maxim ic com 8ETEXVIN MAX3238 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus ABSOLUTE MAXIMUM RATINGS NV GGG thes i cate lle ae r a olan ae 0 3V to 6V VANOS eee cite ctl
6. 000 4000 5000 LOAD CAPACITANCE pF LOAD CAPACITANCE pF LOAD CAPACITANCE pF Pin Description PIN NAME FUNCTION 1 C2 Positive Terminal of Inverting Charge Pump Capacitor 2 GND Ground 3 C2 Negative Terminal of Inverting Charge Pump Capacitor 4 V 5 5V Generated by the Charge Pump 5 6 7 10 12 T_OUT RS 232 Transmitter Outputs T1OUT T50UT 8 9 11 R_IN RS 232 Receiver Inputs R1IN R3IN 13 FORCEON Force Off Input Drive high to override AutoShutdown Plus keeping transmitters and E receivers on FORCEOFF must be high Table 1 14 FORCEOFF Force Off Input Drive low to shut down transmitters receivers except R1OUTB and on board supply This overrides AutoShutdown Plus and FORCEON Table 1 15 INVALID Output of the Valid Signal Detector A logic 1 indicates if a valid RS 232 level is present on receiver inputs 16 R1OUTB Noninverting Complementary Receiver Output Always active 17 19 22 23 24 T_IN TTL CMOS Transmitter Inputs T5IN T1IN 18 20 21 R_OUT TTL CMOS Receiver Outputs R3OUT R10OUT 25 C1 Negative Terminal of Voltage Doubler Charge Pump Capacitor 26 Vcc 3 0V to 5 5V Supply Voltage 27 V 5 5V Generated by the Charge Pump 28 C1 Positive Terminal of Voltage Doubler Charge Pump Capacitor MAXIM 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus Table 1 Output Control Truth Table SORES AUTOSHUTDOWN OPERATION F
7. 19 1144 Rev 1 10 02 M AALS 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus __ General Description The MAX3288 true RS 232 transceiver achieves a 1yuA supply current with Maxim s revolutionary AutoShutdown Plus feature When the device does not sense a valid signal transition on either the receiver or transmitter inputs within 30sec the on board power supply and drivers shut down This occurs if the RS 232 cable is disconnected or if the transmitters of the con nected peripheral are inactive The system turns on again when a valid transition is applied to any RS 232 receiver or transmitter input saving power without changes to the existing BIOS or operating system The MAX3238 5 driver 3 receiver complete serial port is a 8V powered EIA TIA 232 and V 28 V 24 communica tions interface intended for notebook or subnotebook computer applications A proprietary high efficiency dual charge pump power supply and a low dropout transmitter combine to deliver true RS 232 performance from a single 3 0V to 5 5V supply A guaranteed data rate of 250kbps provides compatibility with popu lar software for communicating with personal comput ers The MAX3238 requires only 0 1uF capacitors in 3 3V operation It is ideal for 3 3V only systems mixed 3 3V and 5 0V systems or 5V only systems that require true RS 232 performance Receiver R1 has an extra always active output in addi tion to its standard
8. C4 0 1 uF CLoap 1000pF CLoap 1000pF Figure 7 Loopback Test Result at 120kbps Figure 8 Loopback Test Result at 250kbps Chip Information TRANSISTOR COUNT 1404 10 MAXIM 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus Typical Operating Circuit LOGIC U RS 232 INPUTS OUTPUTS LOGIC OUTPUTS RS 232 INPUTS C3 MAY BE RETURNED TO EITHER Vcc OR GND MAXIM 11 8ETEXVIN 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus 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 DIM INCHES MILLIMETERS MIN MAX MIN MAX A 0 068 0 078 1 73 1 99 MAX3238 A1 0 002 0 008 0 05 0 21 ive 0 010 0 004 0 015 0 25 0 09 0 38 SEE VARIATIONS o mjOIO 0 205 5 20 0 025 0 037 0 0256 BSC 0 65 BSC 0 301 0 311 7 65 7 90 L a o INCHES MIN MAX SSOP SHRINK SMALL OUTLINE PACKAGE 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 ti
9. ORCEON FORCEOFF PLUS STATUS T_OUT R_OUT R10OUTB Shutdown X 0 X Forced Off High Z High Z Active Normal Operation i 1 1 X Forced On Active Active Active Normal 3 Operation 0 1 lt 30sec AutoShutdown Active Active Active Plus Shutdown 0 1 gt 30sec AutoShutdown High Z Active Active Plus X Don t Care Time since last receiver or transmitter input transition Detailed Description Dual Charge Pump Voltage Converter The MAX38238 s internal power supply consists of a reg ulated dual charge pump that provides output voltages of 5 5V doubling charge pump and 5 5V inverting charge pump regardless of the input voltage Vcc over the 3 0V to 5 5V range The charge pumps operate in a discontinuous mode if the output voltages are less than 5 5V the charge pumps are enabled if the output voltages exceed 5 5V the charge pumps are disabled Each charge pump requires a flying capacitor C1 C2 and a reservoir capacitor C3 C4 to generate the V and V supplies RS 232 Transmitters The transmitters are inverting level translators that con vert CMOS logic levels to 5 0V EIA TIA 232 levels The MAX3238 transmitters guarantee a 250kbps data rate with worst case loads of 3kQ in parallel with 1000pF providing compatibility with PC to PC communication software such as LapLink Transmitters can be par alleled to drive multiple receivers Figure 1 shows a complete system connection LapLink i
10. S 232 SIGNAL PRESENT AT ee ANY RECEIVER INPUT INVALID OUTPUT Yes H No L Tables 1 and 2 and Figure 3 summarize the MAX3238 s operating modes FORCEON and FORCEOFF override the automatic circuitry and force the transceiver into its normal operating state or into its low power standby state When neither control is asserted the IC enters AutoShutdown Plus mode and selects between these states automatically based on the last receiver or transmitter input edge received When shut down the device s charge pumps turn off V decays to Vcc V decays to ground and the trans mitter outputs are disabled high impedance The time required to exit shutdown is typically 25us Figure 4b Software Controlled Shutdown If direct software control is desired use INVALID to indicate DTR or Ring Indicator signal Tie FORCEOFF and FORCEON together to bypass the AutoShutdown feature so the line acts like a SHDN input Applications Information Capacitor Selection The capacitor type used for C1 C4 is not critical for proper operation polarized or nonpolarized capacitors can be used The charge pump requires 0 1uF capaci tors for 3 3V operation For other supply voltages see Table 3 for required capacitor values Do not use val ues smaller than those listed in Table 3 Increasing the capacitor values e g by a factor of 2 reduces ripple on the transmitter outputs and slightly reduces power consumption C2 C3 and C4 can be
11. Shutdown Plus Mode uA supply current is achieved with Maxim s AutoShutdown Plus feature which operates when FORCEOFF is high and FORCEON is low When the MAX3238 senses no valid signal transitions on all receiver and transmitter inputs for 30sec the on board power supply and drivers are shut off reducing supply current to 14A This occurs if the RS 232 cable is dis connected or if the connected peripheral transmitters are turned off The system turns on again when a valid transition is applied to any RS 232 receiver or transmit ter input As a result the system saves power without changes to the existing BIOS or operating system The INVALID output is high when the receivers are active Since INVALID indicates the receiver inputs condition it can be used in any mode Figure 3 PREVIOUS RS 232 Tx GND a OLDER RS 232 POWERED DOWN UART DRAWS CURRENT FROM ACTIVE RECEIVER OUTPUT IN SHUTDOWN SHDN GND MAXIM MAX3238 PROTECTION DIODE THREE STATE Til FORCEOFF GN GND b NEW MAX3238 IN SHUTDOWN R1OUTB IS USED TO MONITOR EXTERNAL DEVICES AND R10UT IS THREE STATED ELIMINATING A CURRENT PATH THROUGH THE UART S PROTECTION DIODE Figure 2 The MAX3238 detects RS 232 activity when the UART and interface are shut down MAXIM 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus Table 2 INVALID Truth Table R
12. e 3 Required Minimum Capacitance Values E DETERMINATE ka Vcc C1 C2 C3 C4 CBYPASS V HF HF VALID HIGH 3 0 to 3 6 0 22 0 22 3 15 to 3 6 0 1 0 1 4 5t05 5 0 047 0 33 3 0 to 5 5 0 22 1 Figure 4a Receiver Positive Negative Thresholds for INVALID INVALID ist tAUTOSHDN tAUTOSHDN ALL RECEIVERS TRANSMITTERS INACTIVE ANY ONE RECEIVER TRANSMITTER BECOMES ACTIVE FORCEON GND FORCEOFF Voc Figure 4b AutoShutdown Plus and INVALID Timing Diagram 8 MAXIM 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus Power Supply Decoupling In applications that are sensitive to power supply noise decouple Vcc to ground with a capacitor of the same value as capacitors C2 C3 and C4 Connect the bypass capacitor as close to the IC as possible Transmitter Outputs when Exiting Shutdown Figure 5 shows two transmitter outputs when exiting shutdown mode As they become active the outputs are shown going to opposite RS 232 levels one trans mitter input is high the other is low Each transmitter is loaded with 3kQ in parallel with 2500pF The transmitter outputs display no ringing or undesirable transients as they come out of shutdown Note that the transmitters are enabled only when the magnitude of V exceeds approximately 3V High Data Rates The MAX3238 maintains the RS 232 5 0V minimum transmitter output voltage even at h
13. eceiver Output Enable Time Normal operation 200 ns Receiver Output Disable Time Normal operation 200 ns Transmitter Skew tPHL tPLH 100 ns Receiver Skew tPHL tPLH 50 ns mo CL 150pF to 1000pF 6 30 Transition Region Slew Rate RL 3Q to 7kQ V us e ay E S0pr te 2500pF 4 30 Note 2 A transmitter receiver edge is defined as a transition through the transmitter receiver input logic thresholds MAXIM 3 8ETEXVIN MAX3238 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus Typical Operating Characteristics Vcc 3 3V 250kbps data rate 0 1uF capacitors all transmitters loaded with 3kQ Ta 25 C unless otherwise noted TRANSMITTER OUTPUT VOLTAGE SLEW RATE SUPPLY CURRENT vs LOAD CAPACITANCE vs LOAD CAPACITANCE vs LOAD CAPACITANCE WHEN TRANSMITTING DATA 75 5 14 x 70 z 12 60 3 a Bo z 250kbps z lt a z 10 50 A gt 25 5 FOR DATA RATES UP TO 250kbps 3 B49 120kbps a 1 TRANSMITTER 250kbps M a 0 4 TRANSMITTERS 15 6kbps T 50kbps 2 oc LOADED 3kQ CL 15 6kbps S 30 E 25 a ij Es A 2 Vout S N z 5 0 5 i bps 7 5 0 0 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 0 1000 2000 3
14. igh data rates Figure 6 shows a transmitter loopback test circuit Figure 7 shows a loopback test result at 120kbps and Figure 8 shows the same test at 250kbps For Figure 7 all transmitters were driven simultaneously at 120kbps into RS 232 loads in parallel with 1000pF For Figure 8 a single transmitter was driven at 250kbps and all transmitters were loaded with an RS 282 receiver in parallel with 1000pF FORCEON 2V div a FORCEOFF T20UT 2V div 5us div Vec 3 3V C1 C4 0 1uF Figure 5 Transmitter Outputs when Exiting Shutdown or Powering Up MAXIM Interconnection with 3V and 5V Logic The MAX3238 can directly interface with various 5V logic families including ACT and HCT CMOS See Table 4 for more information on possible combinations of interconnections Table 4 Logic Family Compatibility with Various Supply Voltages SYSTEM Vee POWER SUPPLY SUPPLY VOLTAGE COMPATIBILITY VOLTAGE WV V 3 3 3 3 Compatible with all CMOS families 5 5 Compatible with all TTL and CMOS families Compatible with ACT and HCT 5 3 3 CMOS and with AC HC or CD4000 CMOS MAXIM MAX3238 FORCEON 1000pF FORCEOFF C3 CAN BE RETURNED TO Vcc OR GND Figure 6 Loopback Test Circuit 8ETEXVIN MAX3238 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus Vec 3 3V 2us div Vec 3 3V 2us div C1 C4 0 1 uF C1
15. me 12 Maxim Integrated Products 120 San Gabriel Drive Sunnyvale CA 94086 408 737 7600 2002 Maxim Integrated Products Printed USA MAXIM is a registered trademark of Maxim Integrated Products
16. s a trademark of Traveling Software MAXIM When FORCEOFF is driven to ground the transmitters and receivers are disabled and the outputs go high impedance except for RIOUTB When the Auto Shutdown Plus circuitry senses that all receiver and transmitter inputs are inactive for more than 30sec the transmitters are disabled and the outputs go into a high impedance state but the receivers remain active When the power is off the MAX3238 permits the out puts to be driven up to 12V The transmitter inputs do not have pull up resistors Connect unused inputs to GND or Vcc RS 232 Receivers The receivers convert RS 232 signals to CMOS logic output levels All receivers have inverting three state outputs and are inactive in shutdown FORCEOFF Table 1 The MAX3238 also features an extra always active noninverting output R1OUTB This extra output monitors receiver activity while the other receivers are high impedance allowing Ring Indicator to be moni tored without forward biasing other devices connected to the receiver outputs This is ideal for systems where Vcc is set to OV in shutdown to accommodate peripher als such as UARTs Figure 2 8SEceEXvVN MAX3238 3 0V to 5 5V 1uA up to 250kbps True RS 232 Transceiver with AutoShutdown Plus POWER FORCEOFF FORCEON INVALID MANAGEMENT UNIT OR KEYBOARD CONTROLLER MAXIM MAX3238 Figure 1 Interface Under Control of PMU Auto
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MAXIM MAX3238 handbook