MAX3224EEAP+T

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AVAILABL E Functional Diagrams Pin Configurations appear at end of data sheet. Functional Diagrams continued at end of data sheet. UCSP is a trademark of Maxim Integrated Products, Inc. For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com. 1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus AutoShutdown Plus, MegaBaud, and UCSP are trademarks of Maxim Integrated Products, Inc. ________________General Description The MAX3224–MAX3227/MAX3244/MAX3245 are 3V- powered EIA/TIA-232 and V.28/V.24 communications interfaces with automatic shutdown/wakeup features and high data-rate capabilities. All devices achieve a 1µA supply current using Maxim’s revolutionary AutoShutdown Plus™ feature. These devices automatically enter a low-power shutdown mode when the RS-232 cable is disconnected or the transmitters of the connected peripherals are inactive, and the UART driving the transmitter inputs is inactive for more than 30 seconds. They turn on again when they sense a valid transition at any transmitter or receiv- er input. AutoShutdown Plus saves power without changes to the existing BIOS or operating system. The MAX3225/MAX3227/MAX3245 also feature MegaBaud™ operation, guaranteeing 1Mbps for high- speed applications such as communicating with ISDN modems. The MAX3224/MAX3226/MAX3244 guarantee 250kbps operation. The transceivers have a proprietary low-dropout transmitter output stage enabling true RS- 232 performance from a +3.0V to +5.5V supply with a dual charge pump. The charge pump requires only four small 0.1µF capacitors for operation from a 3.3V supply. The MAX3224–MAX3227 feature a logic-level output (READY) that asserts when the charge pump is regulat- ing and the device is ready to begin transmitting. All devices are available in a space-saving TQFN, TSSOP, and SSOP packages. ________________________Applications Notebook, Subnotebook, and Palmtop Computers Cellular Phones Battery-Powered Equipment Handheld Equipment Peripherals Printers _Next Generation Device Features ♦ For Smaller Packaging: MAX3228/MAX3229: +2.5V to +5.5V RS-232 Transceivers in UCSP™ ♦ For Low-Voltage or Data Cable Applications: MAX3380E/MAX3381E: +2.35V to +5.5V, 1µA, 2 Tx/2 Rx RS-232 Transceivers with ±15kV ESD- Protected I/O and Logic Pins ♦ For Integrated ESD Protection: MAX3222E/MAX3232E/MAX3237E/MAX3241E/ MAX3246E: ±15kV ESD-Protected, Down to 10nA, +3.0V to +5.5V, Up to 1Mbps, True RS-232 Transceivers (MAX3246E Available in UCSP) PART MAX3224 MAX3225 MAX3226 1/1 2/2 2/2 NO. OF DRIVERS/ RECEIVERS READY OUTPUT ✔ ✔ ✔ Auto- Shutdown Plus ✔ ✔ ✔250k 1M 250k GUARANTEED DATA RATE (bps) MAX3227 MAX3244 MAX3245 3/5 3/5 1/1 ✔ — — ✔ ✔ ✔1M 250k 1M _____________________ Selector Guide _______________Ordering Information PART TEMP RANGE PIN-PACKAGE MAX3224CPP+ 0°C to +70°C 20 PDIP MAX3224CAP+ 0°C to +70°C 20 SSOP MAX3224CTP+ 0°C to +70°C 20 TQFN-EP* MAX3224CUP+ 0°C to +70°C 20 TSSOP MAX3224EPP+ -40°C to +85°C 20 PDIP MAX3224EAP+ -40°C to +85°C 20 SSOP MAX3224ETP+ -40°C to +85°C 20 TQFN-EP* MAX3224EUP+ -40°C to +85°C 20 TSSOP +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Ordering Information continued at end of data sheet. 19-1289; Rev 5; 2/11 MAX3224–MAX3227/ MAX3244/MAX3245

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1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus ABSOLUTE MAXIMUM RATINGS ELECTRICAL CHARACTERISTICS (VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°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. VCC to GND..............................................................-0.3V to +6V V+ to GND (Note 1) ..................................................-0.3V to +7V V- to GND (Note 1) ...................................................+0.3V to -7V V+ + ⏐V-⏐(Note 1) ................................................................+13V Input Voltages T_IN, FORCEON, FORCEOFF to GND................ -0.3V to +6V R_IN to GND ....................................................................±25V Output Voltages T_OUT to GND.............................................................±13.2V R_OUT, INVALID, READY to GND .........-0.3V to (VCC + 0.3V) Short-Circuit Duration T_OUT to GND .......................................................Continuous Continuous Power Dissipation (TA = +70°C) 16-Pin SSOP (derate 7.14mW/°C above +70°C) .........571mW 20-Pin PDIP (derate 11.11mW/°C above +70°C) ............889mW 20-Pin TQFN (derate 21.3mW/°C above +70°C)........1702.1mW 20-Pin SSOP (derate 8.00mW/°C above +70°C) .........640mW 20-Pin TSSOP (derate 7.00mW/°C above +70°C) .......559mW 28-Pin SO (W) (derate 12.5mW/°C above +70°C) ............. 1W 28-Pin SSOP (derate 9.52mW/°C above +70°C) .........762mW Operating Temperature Ranges MAX32_ _C_ _.....................................................0°C to +70°C MAX32_ _E_ _..................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10s) .................................+300°C Soldering Temperature (reflow) .......................................+260°C Note 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V. VCC = 5.0V FORCEON = GND, FORCEOFF = VCC, all R_IN idle, all T_IN idle TA = +25°C VCC = 3.3V T_IN, FORCEON, FORCEOFF CONDITIONS kΩ3 5 7Input Resistance V0.5Input Hysteresis 1.8 2.4 V 1.5 2.4 Input Threshold High 0.8 1.5 V 0.6 1.2 Input Threshold Low V-25 +25Input Voltage Range VVCC - 0.6 VCC - 0.1Output Voltage High V0.4Output Voltage Low µA1 10Supply Current, Shutdown µA1 10 Supply Current, AutoShutdown Plus µA±0.05 ±10Output Leakage Current µA±0.01 ±1 Transmitter Input Hysteresis V0.5 V 2.4 Input Logic Threshold High mA0.3 1 Supply Current, AutoShutdown Plus Disabled V0.8Input Logic Threshold Low 2 UNITSMIN TYP MAXSYMBOLPARAMETER FORCEOFF = GND TA = +25°C VCC = 5.0V VCC = 3.3V TA = +25°C R_OUT (MAX3244/MAX3245), receivers disabled T_IN, FORCEON, FORCEOFF VCC = 5.0V FORCEON = FORCEOFF = VCC, no load T_IN, FORCEON, FORCEOFF IOUT = -1.0mA VCC = 3.3V IOUT = 1.6mA DC CHARACTERISTICS (VCC = 3.3V or 5.0V, TA = +25°C) LOGIC INPUTS AND RECEIVER OUTPUTS RECEIVER INPUTS Input Leakage Current 2 Maxim Integrated MAX3224–MAX3227/MAX3244/MAX3245

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1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus ELECTRICAL CHARACTERISTICS (continued) (VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) CONDITIONS Ω300 10MOutput Resistance V±5 ±5.4Output Voltage Swing UNITSMIN TYP MAXSYMBOLPARAMETER Figure 4a T1IN = T2IN = GND, T3IN = VCC, T3OUT loaded with 3kΩ to GND, T1OUT and T2OUT loaded with 2.5mA each s15 30 60tAUTOSHDN Receiver or Transmitter Edge to Transmitters Shutdown µs100tWU Receiver or Transmitter Edge to Transmitters Enabled µs30tINVL Receiver Positive or Negative Threshold to INVALID Low µs1tINVH Receiver Positive or Negative Threshold to INVALID High VVCC - 0.6 INVALID, READY (MAX3224–MAX3227) Output Voltage High V0.4 INVALID, READY (MAX3224–MAX3227) Output Voltage Low V-0.3 0.3 Receiver Input Threshold to INVALID Output Low -2.7 V 2.7Receiver Input Threshold to INVALID Output High V±5Transmitter Output Voltage µA±25Output Leakage Current ±60 mAOutput Short-Circuit Current VCC = V+ = V- = 0, transmitter outputs = ±2V All transmitter outputs loaded with 3kΩ to ground VCC = 5V, Figure 5b (Note 2) VCC = 5V, Figure 5b (Note 2) VCC = 5V, Figure 4b VCC = 5V, Figure 4b IOUT = -1.0mA IOUT = -1.6mA Figure 4a Negative threshold Positive threshold VCC = 0 or 3V to 5.5V, VOUT = ±12V, Transmitters disabled TRANSMITTER OUTPUTS MOUSE DRIVEABILITY (MAX3244/MAX3245) AutoShutdown Plus (FORCEON = GND, FORCEOFF = VCC) Maxim Integrated 3 MAX3224–MAX3227/MAX3244/MAX3245

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1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus TIMING CHARACTERISTICS—MAX3224/MAX3226/MAX3244 (VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) TIMING CHARACTERISTICS—MAX3225/MAX3227/MAX3245 (VCC = +3V to +5.5V, C1–C4 = 0.1µF, tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF, tested at 5.0V ±10%; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) Note 2: A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds. Note 3: Transmitter skew is measured at the transmitter zero cross points. CL = 150pF to 2500pF CL = 150pF to 1000pF R_IN to R_OUT, CL = 150pF RL = 3kΩ, CL = 1000pF, one transmitter switching VCC = 3.3V, TA = +25°C, RL = 3kΩ to 7kΩ, measured from +3V to -3V or -3V to +3V Normal operation (MAX3244 only) Normal operation (MAX3244 only) (Note 3) CONDITIONS 0.15tPLH µs 0.15tPHL kbps250Maximum Data Rate Receiver Propagation Delay V/µs 4 30 6 30 Transition-Region Slew Rate ns200Receiver Output Enable Time ns200Receiver Output Disable Time ns100⏐ tPHL - tPLH ⏐Transmitter Skew ns50⏐ tPHL - tPLH ⏐Receiver Skew UNITSMIN TYP MAXSYMBOLPARAMETER VCC = 4.5V to 5.5V, RL = 3kΩ, CL = 1000pF, one transmitter switching VCC = 3.0V to 4.5V, RL = 3kΩ, CL = 250pF, one transmitter switching RL = 3kΩ, CL = 1000pF, one transmitter switching VCC = 3.3V, TA = +25°C, RL = 3kΩ to 7kΩ, CL = 150pF to 1000pF, measured from +3V to -3V or -3V to +3V (Note 3) R_IN to R_OUT, CL = 150pF Normal operation (MAX3245 only) Normal operation (MAX3245 only) CONDITIONS 1000 1000 kbps 250 Maximum Data Rate V/µs24 150Transition-Region Slew Rate ns50⏐ tPHL - tPLH ⏐Receiver Skew ns25⏐ tPHL - tPLH ⏐Transmitter Skew µs 0.15tPHL Receiver Propagation Delay 0.15tPLH ns200Receiver Output Enable Time ns200Receiver Output Disable Time UNITSMIN TYP MAXSYMBOLPARAMETER 4 Maxim Integrated MAX3224–MAX3227/MAX3244/MAX3245

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1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 0 1000 2000 3000 4000 5000 MAX3224/MAX3226 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 1 LOAD CAPACITANCE (pF) TR A N S M IT TE R O U TP U T V O LT A G E (V ) T1 TRANSMITTING AT 250kbps T2 (MAX3224) TRANSMITTING AT 15.6kbps VOUT+ VOUT- 0 2 4 6 8 10 12 14 16 0 1000 2000 3000 4000 5000 MAX3224/MAX3226 SLEW RATE vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 2 LOAD CAPACITANCE (pF) S LE W R A TE ( V /μ s) -SLEW +SLEW FOR DATA RATES UP TO 250kbps 0 5 10 15 20 25 30 35 40 45 0 20001000 3000 4000 5000 MAX3224/MAX3226 OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 3 LOAD CAPACITANCE (pF) S U P P LY C U R R EN T (m A ) 250kbps 120kbps 20kbps T1 TRANSMITTING AT 250kbps T2 (MAX3224) TRANSMITTING AT 15.6kbps -7.5 0 -2.5 -5.0 2.5 5.0 7.5 0 1000500 1500 2000 2500 MAX3225/MAX3227 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 4 LOAD CAPACITANCE (pF) TR A N S M IT TE R O U TP U T V O LT A G E (V ) 2Mbps 2Mbps 1.5Mbps 1.5Mbps 1Mbps 1Mbps 1 TRANSMITTER AT FULL DATA RATE 1 TRANSMITTER AT 1/16 DATA RATE (MAX3225) LOAD = 3kΩ + CL 0 15 10 5 20 25 30 35 40 45 50 0 1000500 1500 2000 2500 3000 MAX3225/MAX3227 TRANSMITTER SKEW vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 7 LOAD CAPACITANCE (pF) TR A N S M IT TE R S K EW ( ns ) AVERAGE; 10 PARTS 1 TRANSMITTER AT 512kbps 1 TRANSMITTER AT 30kbps (MAX3225) LOAD = 3kΩ + CL 0 80 70 60 50 40 30 20 10 0 500 1000 1500 2000 2500 MAX3225/MAX3227 SLEW RATE vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 5 LOAD CAPACITANCE (pF) S LE W R A TE ( V /μ s) 1 TRANSMITTER AT 1Mbps 1 TRANSMITTER AT 62.5kbps (MAX3225) -SLEW +SLEW 0 20 10 40 30 60 50 70 90 80 100 0 500 1000 1500 2000 2500 MAX3225/MAX3227 OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE M A X 3 2 2 4 -0 6 LOAD CAPACITANCE (pF) S U P P LY C U R R EN T (m A ) 2Mbps 1.5Mbps 1Mbps 1 TRANSMITTER AT FULL DATA RATE 1 TRANSMITTER AT 1/16 DATA RATE (MAX3225) LOAD = 3kΩ + CL 20 24 22 30 28 26 36 34 32 38 -40 0 20-20 40 60 80 100 MAX3224–MAX3227 READY TURN-ON TIME vs. TEMPERATURE M A X 3 2 2 4 -0 8 TEMPERATURE (°C) R EA D Y T U R N -O N T IM E (μ s) 0 200 180 160 140 120 100 80 60 40 20 -40 0 20-20 40 60 80 100 MAX3224–MAX3227 READY TURN-OFF TIME vs. TEMPERATURE M A X 3 2 2 4 -0 9 TEMPERATURE (°C) R EA D Y T U R N -O FF T IM E (n s) __________________________________________Typical Operating Characteristics (VCC = +3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.) Maxim Integrated 5 MAX3224–MAX3227/MAX3244/MAX3245

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1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus Typical Operating Characteristics (continued) (VCC = +3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ and CL, TA = +25°C, unless otherwise noted.) -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 0 1000 2000 3000 4000 5000 MAX3244 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 0 LOAD CAPACITANCE (pF) TR A N S M IT TE R O U TP U T V O LT A G E (V ) 1 TRANSMITTER AT 250kbps 2 TRANSMITTERS AT 15.6kbps VOUT+ VOUT- 0 4 2 8 6 12 10 14 0 1000 2000 3000 4000 5000 MAX3244 SLEW RATE vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 1 LOAD CAPACITANCE (pF) S LE W R A TE ( V /μ s) 0 30 20 10 40 50 60 0 20001000 3000 4000 5000 MAX3244 OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 2 LOAD CAPACITANCE (pF) S U P P LY C U R R EN T (m A ) 250kbps 120kbps 20kbps 1 TRANSMITTER AT 250kbps 2 TRANSMITTERS AT 15.6kbps -7.5 0 -2.5 -5.0 2.5 5.0 7.5 0 800400 1200 1600 2000 MAX3245 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 3 LOAD CAPACITANCE (pF) TR A N S M IT TE R O U TP U T V O LT A G E (V ) 2Mbps 2Mbps 1.5Mbps 1.5Mbps 1Mbps 1Mbps 1 TRANSMITTER AT FULL DATA RATE 2 TRANSMITTERS AT 1/16 DATA RATE 0 20 10 40 30 60 50 70 90 80 100 0 400 800 1200 1600 2000 MAX3245 OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 5 LOAD CAPACITANCE (pF) S U P P LY C U R R EN T (m A ) 2Mbps 1.5Mbps 1Mbps 1 TRANSMITTER AT FULL DATA RATE 2 TRANSMITTERS AT 1/16 DATA RATE 0 20 10 40 30 60 50 70 0 400 800 1200 1600 2000 MAX3245 SLEW RATE vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 4 LOAD CAPACITANCE (pF) S LE W R A TE ( V /μ s) 1 TRANSMITTER AT 1Mbps 2 TRANSMITTERS AT 62.5kbps 0 15 10 5 20 25 30 35 40 45 50 0 1000 2000 3000 MAX3245 TRANSMITTER SKEW vs. LOAD CAPACITANCE M A X 3 2 2 4 -1 6 LOAD CAPACITANCE (pF) TR A N S M IT TE R S K EW ( ns ) 6 Maxim Integrated MAX3224–MAX3227/MAX3244/MAX3245

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_______________Detailed Description Dual Charge-Pump Voltage Converter The MAX3224–MAX3227/MAX3244/MAX3245’s internal power supply consists of a regulated dual charge pump that provides output voltages of +5.5V (doubling charge pump) and -5.5V (inverting charge pump), over the +3.0V to +5.5V range. The charge pump operates in discontinuous mode: if the output voltages are less than 5.5V, the charge pump is enabled; if the output voltages exceed 5.5V, the charge-pump is disabled. Each charge pump requires a flying capacitor (C1, C2) and a reservoir capacitor (C3, C4) to generate the V+ and V- supplies. The READY output (MAX3224–MAX3227) is low when the charge pumps are disabled in shutdown mode. The READY signal asserts high when V- goes below -4V. 1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus Pin Description PIN MAX3224 MAX3225 PDIP/ SSIP/ TSSOP TQFN- EP MAX3226 MAX3227 MAX3244 MAX3245 NAME FUNCTION 1 19 1 — READY Ready to Transmit Output, Active High. READY is enabled high when V- goes below -4V and the device is ready to transmit. 2 1 2 28 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor 3 20 3 27 V+ +5.5V Generated By the Charge Pump 4 2 4 24 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor 5 3 5 1 C2+ Positive Terminal of Inverting Charge-Pump Capacitor 6 4 6 2 C2- Negative Terminal of Inverting Charge-Pump Capacitor 7 5 7 3 V- -5.5V Generated By the Charge Pump 8, 17 6, 15 13 9, 10, 11 T_OUT RS-232 Transmitter Outputs 9, 16 7, 14 8 4–8 R_IN RS-232 Receiver Inputs 10, 15 8, 13 9 15–19 R_OUT TTL/CMOS Receiver Outputs 11 9 10 21 INVALID Valid Signal Detector Output, Active Low. A logic-high indicates that a valid RS-232 level is present on a receiver input. 12, 13 10, 11 11 12, 13, 14 T_IN TTL/CMOS Transmitter Inputs 14 12 12 23 FORCEON Force-On Input, Active High. Drive high to override AutoShutdown Plus, keeping transmitters and receivers on (FORCEOFF must be high) (Table 1). 18 16 14 25 GND Ground 19 17 15 26 VCC +3.0V to +5.5V Single Supply Voltage 20 18 16 22 FORCEOFF Force-Off Input, Active Low. Drive low to shut down transmitters, receivers (except R2OUTB), and charge pump. This overrides AutoShutdown Plus and FORCEON (Table 1). — — — 20 R2OUTB TTL/CMOS Noninverting Complementary Receiver Outputs. Always active. — — — — EP Exposed Pad (TQFN only). Solder the exposed pad to the ground, or leave unconnected. Maxim Integrated 7 MAX3224–MAX3227/MAX3244/MAX3245

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RS-232 Transmitters The transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The MAX3224/MAX3226/MAX3244 guarantee a 250kbps data rate (1Mbps for the MAX3225/MAX3227/ MAX3245) with worst-case loads of 3kΩ in parallel with 1000pF, providing compatibility with PC-to-PC com- munication software (such as LapLink®). Transmitters can be paralleled to drive multiple receivers. Figure 1 shows a complete system connection. When FORCEOFF is driven to ground or 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. When powered off or shut down, the outputs can be driven to ±12V. The transmitter inputs do not have pull-up resistors. Connect unused inputs to GND or VCC. 1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus MAX3244 MAX3245 I/O CHIP WITH UART CPU RS-232 POWER- MANAGEMENT UNIT OR KEYBOARD CONTROLLER FORCEOFF FORCEON INVALID Figure 1. Interface Under Control of PMU MAX3244 MAX3245 T1OUT R2OUTB Tx 5kΩUART VCC T1IN THREE-STATED LOGIC TRANSITION DETECTOR R2IN PROTECTION DIODE R2OUT FORCEOFF = GND VCC TO μP Rx PREVIOUS RS-232 Tx UART SHDN = GND VCC VCC GND Rx 5kΩ a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE RECEIVER OUTPUT IN SHUTDOWN. b) NEW MAX3244/MAX3245: IN SHUTDOWN, R2OUTB IS USED TO MONITOR EXTERNAL DEVICES AND R2OUT IS THREE STATED, ELIMINATING A CURRENT PATH THROUGH THE UART’S PROTECTION DIODE. GND PROTECTION DIODE I I Figure 2. The MAX3244/MAX3245 detect RS-232 activity when the UART and interface are shut down. LapLink is a registered trademark of Laplink Software, Inc. 8 Maxim Integrated MAX3224–MAX3227/MAX3244/MAX3245

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RS-232 Receivers The receivers convert RS-232 signals to CMOS-logic output levels. The MAX3224–MAX3227 feature inverting outputs that always remain active (Table 1). The MAX3244/MAX3245 have inverting three-state outputs that are high impedance when shut down (FORCEOFF = GND) (Table 1). The MAX3244/MAX3245 feature an extra, always active, noninverting output, R2OUTB. R2OUTB output monitors receiver activity while the other receivers are high impedance, allowing Ring Indicator applications to be monitored without forward biasing other devices connected to the receiver outputs. This is ideal for sys- tems where VCC is set to ground in shutdown to accommodate peripherals such as UARTs (Figure 2). The MAX3224–MAX3227/MAX3244/MAX3245 feature an INVALID output that is enabled low when no valid RS-232 voltage levels have been detected on all receiv- er inputs. Because INVALID indicates the receiver input’s condition, it is independent of FORCEON and FORCEOFF states (Figures 3 and 4). AutoShutdown Plus Mode The MAX3224–MAX3227/MAX3244/MAX3245 achieve a 1µA supply current with Maxim’s AutoShutdown Plus feature, which operates when FORCEOFF is high and a FORCEON is low. When these devices do not sense a valid signal transition on any receiver and transmitter input for 30sec, the on-board charge pumps are shut down, reducing supply current to 1µA. This occurs if the RS-232 cable is disconnected or if the connected 1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceivers with AutoShutdown Plus Table 1. Output Control Truth Table OPERATION STATUS FORCEON FORCEOFF VALID RECEIVER LEVEL RECEIVER OR TRANSMITTER EDGE WITHIN 30sec T_OUT R_OUT (MAX3224/ MAX3225/ MAX3226/ MAX3227) R_OUT (MAX3244/ MAX3245) R2OUTB (MAX3244/ MAX3245) Shutdown (Forced Off) X 0 X X High-Z Active High-Z Active Normal Operation (Forced On) 1 1 X X Active Active Active Active Normal Operation (AutoShutdown Plus) 0 1 X Yes Active Active Active Active Shutdown (Auto- Shutdown Plus) 0 1 X No High-Z Active Active Active Normal Operation INVALID* 1 Yes X Active Active Active Active Normal Operation INVALID* 1 X Yes Active Active Active Active Shutdown INVALID* 1 No No High-Z Active Active Active Normal Operation (AutoShutdown) INVALID* INVALID** Yes X Active Active Active Active Shutdown (AutoShutdown™) INVALID* INVALID** No X High-Z Active High-Z Active X = Don’t care *INVALID connected to FORCEON **INVALID connected to FORCEON and FORCEOFF AutoShutdown is a trademark of Maxim Integrated Products, Inc. Maxim Integrated 9 MAX3224–MAX3227/MAX3244/MAX3245