±15kV ESD-Protected, 1µA, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors

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1 ; Rev 2; 8/4 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual General Description The are EIA/TIA-232 and.28/.24 communications interfaces with automatic shutdown/ wake-up features, high data-rate capabilities, and enhanced electrostatic discharge (ESD) protection. All transmitter outputs and receiver inputs are protected to ±15k using IEC Air-Gap Discharge, to ±8k using IEC Contact Discharge, and to ±15k using the Human Body Model. The operates from a +3.3 supply; the operates from +5.. 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 following two conditions occur: either 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 3 seconds. They turn on again when they sense a valid transition at any transmitter or receiver input. AutoShutdown Plus saves power without changes to the existing BIOS or operating system. The have internal dual charge pumps requiring no external capacitors. Both transceivers have a proprietary low-dropout transmitter output stage that enables true RS-232 performance from a +3. to +3.6 supply for the or a +4.5 to +5.5 supply for the. These devices are guaranteed to operate up to 25kbps. Both are available in space-saving 2-pin wide SO or plastic DIP packages. Applications Subnotebook and Palmtop Computers Cellular Phones Battery-Powered Equipment Handheld Equipment Peripherals Embedded Systems Ordering Information PART TEMP RANGE PIN-PACKAGE CWP C to +7 C 2 SO CPP C to +7 C 2 Plastic DIP EWP -4 C to +85 C 2 SO EPP -4 C to +85 C 2 Plastic DIP Ordering Information continued at end of data sheet. AutoShutdown Plus is a trademark of Maxim Integrated Products, Inc. Co7; 4,7er pg. Features ESD Protection for RS-232 I/O Pins ±15k Human Body Model ±8k IEC 1-4-2, Contact Discharge ±15k IEC 1-4-2, Air-Gap Discharge Latchup Free 1µA Supply Current AutoShutdown Plus 1997 EDN Magazine Innovation of the Year Single-Supply Operation +3. to +3.6 () +4.5 to +5.5 () 25kbps Guaranteed Data Rate 6/µs Guaranteed Slew Rate Meets EIA/TIA-232 Specifications Down to 3. () Internal Charge-Pump Capacitors R2OUT INALID T2IN T1IN R1OUT T1OUT R1IN CC Pin Configuration/ Functional Diagram CHARGE PUMP SO/DIP Typical Operating Circuit appears at end of data sheet R2IN T2OUT GND - C2+ C2- C1- C Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual ABSOLUTE MAXIMUM RATINGS CC to GND () to +4 CC to GND () to +6 + to GND (Note 1) to +7 - to GND (Note 1) to (Note 1) Input oltages T_IN,, to GND to +6 R_IN to GND...±25 Output oltages T_OUT to GND...±13.2 R_OUT, INALID to GND to ( CC +.3) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS Short-Circuit Duration T_OUT to GND...Continuous Continuous Power Dissipation (T A = +7 C) Wide SO (derate 1mW/ C above +7 C)...8mW Plastic DIP (derate 11.11mW/ C above +7 C)...889mW Operating Temperature Ranges MAX323_EC_P... C to +7 C MAX323_EE_P...-4 C to +85 C Storage Temperature Range C to +15 C Lead Temperature (soldering, 1s) (Note 2)...+3 C Note 1: + and - can have maximum magnitudes of 7, but their absolute difference cannot exceed 13. Note 2: Maximum reflow temperature is +22 C. ( CC = +3. to +3.6 for, CC = +4.5 to +5.5 for ; T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) PARAMETER SYMBOL CONDITIONS DC CHARACTERISTICS ( CC = 3.3 for, CC = 5. for, T A = +25 C. ) Supply Current, AutoShutdown Plus Supply Current, Shutdown Supply Current, AutoShutdown Plus Disabled LOGIC INPUTS AND RECEIER OUTPUTS Input Logic Threshold Low Input Logic Threshold High Transmitter Input Hysteresis Input Leakage Current Output oltage Low Output oltage High RECEIER INPUTS Input oltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance = GND, = CC, all R_IN idle, all T_IN idle = GND = = CC, no load T_IN,, T_IN,, CC = 3.3, CC = 5., T_IN,, I OUT = 1.6mA I OUT = -1.mA T A = +25 C T A = +25 C T A = +25 C CC = 3.3, CC = 5., CC = 3.3, CC = 5., MIN TYP MAX ±.1 ±1.4 CC -.6 CC UNITS µa µa ma µa kω 2

3 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual ELECTRICAL CHARACTERISTICS (continued) ( CC = +3. to +3.6 for, CC = +4.5 to +5.5 for ; T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) PARAMETER TRANSMITTER OUTPUTS Output oltage Swing Output Resistance Output Short-Circuit Current Output Leakage Current Receiver or Transmitter Edge to Transmitters Enabled SYMBOL t WU CONDITIONS ESD PROTECTION IEC1-4-2 Air Discharge R_IN, T_OUT IEC1-4-2 Contact Discharge Human Body Model AutoShutdown PLUS ( = GND, = CC ) Receiver Input Threshold to Positive threshold Figure 3a INALID Output High Negative threshold Receiver Input Threshold to INALID Output Low Figure 3a INALID Output oltage Low I OUT = -1.6mA INALID, Output oltage High I OUT = -1.mA Receiver Positive or Negative Threshold to INALID High t INH Figure 3b Receiver Positive or Negative Threshold to INALID Low t INL All transmitter outputs loaded with 3kΩ to ground CC = + = - =, transmitter outputs = ±2 OUT = ± 12 transmitters disabled Figure 3b Figure 3b (Note 3) CC = or +3. to 3.6 () CC = or +4.5 to 5.5 () MIN TYP MAX ±5 ± M CC -.6 ±15 ±8 ± UNITS Ω ±6 ma ±25 ± µa k µs µs µs Receiver or Transmitter Edge to Transmitters Shut Down t AUTOSHDN Figure 3b (Note 3) s Note 3: A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds. 3

4 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual TIMING CHARACTERISTICS ( CC = +3. to +3.6 for, CC = +4.5 to +5.5 for ; T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Maximum Data Rate R L = 3kΩ, C L = 1pF, one transmitter switching 25 kbps 7 Receiver Propagation Delay t PHL Receiver Output Enable Time Receiver Output Disable Time Transmitter Skew t PHL - t PLH Receiver Skew t PLH t PHL - t PLH R_IN to R_OUT, C L = 15pF Normal operation Normal operation (Note 4) CC = 3.3 (), C L = 15pF CC = 5. (), 6 3 to 1pF T A = +25 C, Transition-Region Slew Rate Note 2: A transmitter/receiver edge is defined as Ra L transition = 3kΩ to 7kΩ, through the transmitter/receiver input logic thresholds. Note 3: Transmitter skew is measured at the transmitter measured zero from cross +3 points. to -3 C L = 15pF 4 3 or -3 to +3 to 25pF ns ns ns ns ns ns /µs Note 4: Transmitter skew is measured at the transmitter zero crosspoints. Typical Operating Characteristics ( CC = +3.3 for, CC = +5. for ; 25kbps data rate; all transmitters loaded with 3kΩ and C L ; T A = +25 C, unless otherwise noted.) TRANSMITTER OUTPUT OLTAGE () TRANSMITTER OUTPUT OLTAGE vs. LOAD CAPACITANCE OUT + OUT - /35Etoc1 SUPPLY CURRENT (ma) OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE TRANSMITTER 1 AT DATA RATE TRANSMITTER 2 AT 1/16 DATA RATE 25kbps 12kbps 2kbps /35E toc2 SLEW RATE (/µs) SLEW RATE vs. LOAD CAPACITANCE SLEW RATE - SLEW RATE + /35Etoc LOAD CAPACITANCE (pf) LOAD CAPACITANCE (pf) LOAD CAPACITANCE (pf) 4

5 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual Pin Description PIN NAME FUNCTION 1 R2OUT TTL/CMOS Receiver Outputs 6 R1OUT Invalid Signal Detector Output, active low. A logic high indicates that a valid RS INALID level is present on a receiver. 3 T2IN TTL/CMOS Transmitter Outputs 4 T1IN Force-On Input, active high. Drive high to override AutoShutdown Plus, keeping 5 transmitters and receivers active ( must be high) (Table 1). 7 T1OUT RS-232 Transmitter Outputs 19 T2OUT 8 R1IN RS-232 Receiver Outputs 2 R2IN 9 CC Supply oltage ( = +3.3, = +5.) Force-Off Input, active low. Drive low to shut down transmitters, receivers, and charge 1 pump. This overrides AutoShutdown Plus and (Table 1). 11, generated by the charge pump. Do not connect. Positive terminal of the internal voltage-doubling charge-pump capacitor. Leave 13 C1+ unconnected or connect to an external.1µf capacitor. See Charge Pump Section C1- Negative terminal of the internal voltage-doubling charge-pump capacitor. Leave unconnected or connect to an external.1µf capacitor. See Charge Pump Section. C2+ Positive terminal of the internal inverting charge-pump capacitor. Do not connect. C2- Negative terminal of the internal inverting charge-pump capacitor. Do not connect generated by the charge pump. Do not connect. GND Ground 5

6 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual Detailed Description Dual Charge-Pump oltage Converter The s internal power supply consists of a regulated dual charge pump that provides output voltages of +5.5 (doubling charge pump) and -5.5 (inverting charge pump), with no external capacitors. The charge pump operates in discontinuous mode: if the output voltages are less than 5.5, the charge pump is enabled; if the output voltages exceed 5.5, the charge pump is disabled. RS-232 Transmitters The transmitters are inverting level translators that convert CMOS-logic levels to 5. EIA/TIA-232 levels. The devices guarantee a 25kbps data rate with worstcase loads of 3kΩ in parallel with 1pF, providing compatibility with PC-to-PC communication software (such as LapLink ). Transmitters can be paralleled to drive multiple receivers. Figure 1 shows a complete system connection. When is driven to ground or when the Auto- Shutdown Plus circuitry senses that all receiver and transmitter inputs are inactive for more than 3sec, the transmitters are disabled and the outputs go into a highimpedance state. When powered off or shut down, the outputs can be driven to ±12. The transmitter inputs do not have pull-up resistors. Connect unused inputs to GND or CC. RS-232 Receivers The receivers convert RS-232 signals to CMOS-logic output levels. They feature inverting outputs that always remain active (Table 1). The feature an INALID output that is enabled low when no valid RS-232 voltage levels have been detected on all receiver inputs. Because INALID indicates the receiver input s condition, it is independent of and states (Figures 2 and 3). AutoShutdown Plus Mode The devices achieve a 1µA supply current with Maxim s AutoShutdown Plus feature, which operates when is high and a is low. When these devices do not sense a valid signal transition on any receiver or transmitter input for 3sec, 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 peripheral transmitters are turned off and the UART driving the transmitter inputs is inactive. The system turns on again when a valid transition is LapLink is a trademark of Traveling Software. POWER- MANAGEMENT UNIT OR KEYBOARD CONTROLLER CPU INALID I/O CHIP WITH UART Figure 1. Interface Under Control of PMU +.3 R_IN -.3 8µs TIMER R INALID RS-232 INALID ASSERTED IF ALL RECEIER INPUTS ARE BETWEEN +.3 AND -.3 FOR AT LEAST 8µs. Figure 2a. INALID Functional Diagram, INALID Low +2.7 R_IN µs TIMER R INALID INALID DEASSERTED IF ANY RECEIER INPUT HAS BEEN ABOE +2.7 OR BELOW -2.7 FOR 1µs. Figure 2b. INALID Functional Diagram, INALID High 6

7 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual Table 1. Output Control Truth Table OPERATION STATUS ALID RECEIER LEEL Rx or Tx EDGE WITHIN 3sec T_OUT R_OUT Shutdown (Forced Off) X X X High-Z Active Normal Operation (Forced On) 1 1 X X Active Active Normal Operation (AutoShutdown Plus) Shutdown (AutoShutdown Plus) 1 X Yes Active Active 1 X No High-Z Active Normal Operation INALID* 1 Yes X Active Active Normal Operation INALID* 1 X Yes Active Active Shutdown INALID* 1 No No High-Z Active Normal Operation (AutoShutdown) INALID* INALID** Yes X Active Active Shutdown (AutoShutdown) INALID* INALID** No X High-Z Active X = Don t care * INALID connected to ** INALID connected to and T_IN R_IN EDGE DETECT EDGE DETECT S 3sec TIMER R AUTOSHDN* AUTOSHDN POWERDOWN* *AUTOSHDN IS ONLY AN INTERNAL SIGNAL. Figure 2c. AutoShutdown Plus Logic applied to any RS-232 receiver or transmitter input. As a result, the system saves power without changes to the existing BIOS or operating system. Figures 2a and 2b depict invalid and valid RS-232 receiver voltage levels. INALID indicates the receiver input s condition, and is independent of and states. Figure 2 and Tables 1 and 2 summarize the operating modes. and FORCE- * POWERDOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES. Figure 2d. Power-Down Logic OFF override AutoShutdown Plus circuitry. When neither control is asserted, the IC 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, + is pulled to CC, - is pulled to ground, and the transmitter outputs are high impedance. The time required to exit shutdown is typically 1µs (Figure 7). 7

8 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual By connecting to INALID, the device shuts down when no valid receiver level and no receiver or transmitter edge is detected for 3sec. It wakes up when a valid receiver level or receiver or transmitter edge is detected. By connecting and to INALID, the device shuts down when no valid receiver level is detected and wakes up when a valid receiver level is detected. A system with AutoShutdown Plus may need time to wake up. Figure 4 shows a circuit that forces the transmitters on for 1ms, allowing enough time for another system to realize that the / RECEIER INPUT LEELS () INALID HIGH INDETERMINATE INALID LOW INDETERMINATE INALID HIGH Figure 3a. Receiver Positive/Negative Thresholds for INALID is awake. If another system outputs valid RS-232 signal transitions within that time, the RS-232 ports on both systems remain enabled. Software-Controlled Shutdown If direct software control is desired, use INALID to indicate DTR or Ring Indicator signal. Tie and together to bypass the AutoShutdown Plus so the line acts like a SHDN input. ±15k ESD Protection As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver outputs and receiver inputs have extra protection against static electricity. Maxim s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15k without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD Table 2. INALID Truth Table RS-232 SIGNAL PRESENT AT ANY RECEIER INPUT Yes No INALID OUTPUT High Low RECEIER INPUTS } INALID REGION TRANSMITTER INPUTS TRANSMITTER OUTPUTS INALID OUTPUT CC t INL t INH t t AUTOSHDN AUTOSHDN t WU t WU + CC - Figure 3b. AutoShutdown Plus, INALID, and READY Timing Diagram 8

9 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual POWER- MANAGEMENT UNIT MASTER SHDN LINE.1µF 1MΩ Figure 4. AutoShutdown Plus Initial Turn-On to Wake Up Another System HIGH- OLTAGE DC SOURCE R C 1MΩ CHARGE-CURRENT LIMIT RESISTOR Cs 1pF R D 15Ω DISCHARGE RESISTANCE STORAGE CAPACITOR DEICE UNDER TEST HIGH- OLTAGE DC SOURCE R C 5MΩ to 1MΩ CHARGE CURRENT LIMIT RESISTOR Cs 15pF R D 33Ω DISCHARGE RESISTANCE STORAGE CAPACITOR Figure 6a. IEC ESD Test Model DEICE UNDER TEST ESD protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family are characterized for protection to the following limits: 1) ±15k using the Human Body Model 2) ±8k using the Contact Discharge method specified in IEC ) ±15k using IEC s Air-Gap Discharge method ESD Test Conditions ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results. Figure 5a. Human Body ESD Test Model AMPERES I P 1% 9% Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) Human Body Model Figure 5a shows the Human Body Model and Figure 5b shows the current waveform it generates when discharged into a low impedance. This model consists of a 1pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5kΩ resistor. 36.8% 1% t RL TIME t DL CURRENT WAEFORM Figure 5b. Human Body Current Waveform event, Maxim s E versions keep working without latchup, whereas competing RS-232 products can latch and must be powered down to remove latchup. IEC The IEC standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The help you design equipment that meets Level 4 (the highest level) of IEC 1-4-2, without the need for additional ESD-protection components. The major difference between tests done using the Human Body Model and IEC is higher peak current in IEC 1-4-2, because series resistance is lower in the IEC model. Hence, the ESD withstand voltage measured to IEC is generally lower than 9

10 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual IPEAK I 1% 9% 1% tr =.7ns to 1ns t 3ns 6ns Figure 6b. IEC ESD Generator Current Waveform CC CC C BYPASS T_ IN R_ OUT CC GND T_ OUT R_ IN 5kΩ 1pF 5/div 2/div 1/div = CC = 3.3 1µs/div Figure 7. Transmitter Outputs when Exiting Shutdown or Powering Up T1OUT T2OUT that measured using the Human Body Model. Figure 6a shows the IEC model, and Figure 6b shows the current waveform for the ±8k, IEC 1-4-2, Level 4, ESD contact-discharge test. The air-gap test involves approaching the device with a charged probe. The contact-discharge method connects the probe to the device before the probe is energized. Machine Model The Machine Model for ESD tests all pins using a 2pF storage capacitor and zero discharge resistance. Its objective is to emulate the stress caused by contact that occurs with handling and assembly during Figure 8. Loopback Test Circuit manufacturing. Of course, all pins require this protection during manufacturing, not just RS-232 inputs and outputs. Therefore, after PC board assembly, the Machine Model is less relevant to I/O ports. Applications Information Charge Pumps The do not require external capacitors to operate their internal charge pumps. The can be operated down to 3. by paralleling the internal C1 capacitor with an external.1µf. When using an external capacitor across the C1 terminals, check to confirm that the total supply voltage measured from + to - does not exceed the absolute maximum voltage of 13. With the external.1µf capacitor added, the should not be used with a supply greater than Power-Supply Decoupling In most applications, a.1µf CC bypass capacitor is adequate. Connect bypass capacitors as close to the IC as possible. Transmitter Outputs when Exiting Shutdown Figure 7 shows two transmitter outputs when exiting shutdown mode. As they become active, the two transmitter outputs are shown going to opposite RS-232 levels (one transmitter input is high, the other is low). 1

11 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual Each transmitter is loaded with 3kΩ in parallel with 1pF. 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 - exceeds approximately -3. High Data Rates The maintain the RS-232 ±5. minimum transmitter output voltage even at high data rates. Figure 8 shows a transmitter loopback test circuit. Figure 9 shows a loopback test result at 12kbps, and Figure 1 shows the same test at 25kbps. For T1IN T1OUT 5/div 5/div Figure 9, all transmitters were driven simultaneously at 12kbps into RS-232 loads in parallel with 1pF. For Figure 1, a single transmitter was driven at 25kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 25pF. Interconnection with 3 and 5 Logic The can directly interface with various 5 logic families, including ACT and HCT CMOS. See Table 3 for more information on possible combinations of interconnections. T1IN T1OUT 5/div 5/div R1OUT CC = 3.3 (), CC = 5. () 5/div R1OUT CC = 3.3 (), CC = 5. () 5/div 2µs/div 2µs/div Figure 9. Loopback Test Result at 12kbps Figure 1. Loopback Test Result at 25kbps Table 3. Logic Family Compatibility with arious Supply oltages DEICE LOGIC POWER-SUPPLY OLTAGE () CC SUPPLY OLTAGE () COMPATIBILITY /5 5 Compatible with all CMOS families Compatible with ACT and HCT CMOS, and with AC, HC, or CD4 CMOS Compatible with all TTL and CMOS families 11

12 ±15k ESD-Protected, 1µA, 25kbps, 3.3/5, Dual C BYPASS TTL/CMOS INPUTS TTL/CMOS OUTPUTS CC.1µF C1+ C2- C1- C2+ T1IN T2IN R1OUT R2OUT Typical Operating Circuit 9 CC 5kΩ 5kΩ + - T1OUT 7 T2OUT 19 R1IN 8 R2IN 2 11, RS-232 OUTPUTS RS-232 INPUTS Ordering Information (continued) PART TEMP RANGE PIN-PACKAGE CWP CPP Chip Information TRANSISTOR COUNT: 1129 C to +7 C 2 SO C to +7 C EWP -4 C to +85 C 2 SO 2 Plastic DIP EPP -4 C to +85 C 2 Plastic DIP Package Information For the latest package outline information, go to AUTOSHUTDOWN PLUS INALID CC GND 18 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circu it patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.