19-1632; Rev 1; 6/01 +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins All RS-232 inputs and outputs, as well as the logic I/O pins, have enhanced ESD protection to ±15kV. The additional ESD protection on the logic I/O pins makes the MAX3238E/MAX3248E ideal for cell phone data cable applications because it eliminates the need for costly external TransZorb™ or protection schemes. The MAX3238E/MAX3248E contain five drivers and three receivers and are 3V-powered EIA/TIA-232 and V.28/V.24 communication interfaces intended for cell phones, data cables, and modem applications. A proprietary, high-efficiency, dual charge-pump power supply and a lowdropout 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 popular software for communicating with personal computers. The MAX3238E and the MAX3248E differ only in their input logic thresholds. The MAX3238E has standard logic thresholds, while the MAX3248E has low-level logic thresholds of 0.6V to 1.2V, which are ideal for 1.8V systems. The transmitter inputs, FORCEON, and FORCEOFF have a 400kΩ active positive feedback resistor. Once driven to a valid logic level, they will retain this level if the driving signal is removed or goes high impedance. Unused transmitter and logic inputs may be left unconnected. The MAX3238E/MAX3248E can operate with supply voltages ranging from +3.0V to +5.5V. Applications Cellular Data Cables Modems Battery-Powered Equipment Peripherals Data Cradles Printers AutoShutdown Plus is a trademark of Maxim Integrated Products. TransZorb is a trademark of General Semiconductor Industries, Inc. †Covered by U.S. Patent numbers 4,636,930; 4,679,134; 4,777,577; 4,797,899; 4,809,152; 4,897,774; 4,999,761; and other patents pending. Features ♦ Enhanced ESD Protection on RS-232 I/O Pins and All Logic Pins ±15kV—Human Body Model ±8kV—IEC 1000-4-2 Contact Discharge ±15kV—IEC 1000-4-2 Air-Gap Discharge ♦ Guaranteed Data Rate: 250kbps ♦ 10nA Low-Power Shutdown with Receivers Active ♦ Schmitt Triggers on All Inputs ♦ Flow-Through Pinout ♦ Meets EIA/TIA-232 Specifications Down to 3.0V ♦ Guaranteed 6V/µs Slew Rate ♦ Low-Level Logic Thresholds (MAX3248E) ♦ RS-232-Compatible Outputs to 2.7V Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX3238ECAI 0°C to +70°C 28 SSOP MAX3238EEAI -40°C to +85°C 28 SSOP MAX3248ECAI 0°C to +70°C 28 SSOP MAX3248EEAI -40°C to +85°C 28 SSOP Typical Operating Circuit appears at end of data sheet. ___________________Pin Configuration TOP VIEW C2+ 1 GND 2 27 V+ C2- 3 26 VCC 25 C1- 28 C1+ V- 4 T1OUT 5 T2OUT 6 T3OUT 7 22 T3IN R1IN 8 21 R1OUT R2IN 9 24 T1IN MAX3238E MAX3248E 23 T2IN 20 R2OUT 19 T4IN T4OUT 10 18 R3OUT R3IN 11 17 T5IN T5OUT 12 FORCEON 13 16 R1OUTB FORCEOFF 14 15 INVALID SSOP ________________________________________________________________ Maxim Integrated Products 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. 1 MAX3238E/MAX3248E† General Description The MAX3238E/MAX3248E transceivers use Maxim’s revolutionary AutoShutdown Plus™ feature to achieve 10nA supply current. These devices shut down the onboard power supply and drivers when they do not sense a valid signal transition on either the receiver or transmitter inputs. This occurs if the RS-232 cable is disconnected or if the transmitters of the connected peripheral are turned off. The devices turn on again when a valid transition is applied to any RS-232 receiver or transmitter input. AutoShutdown Plus automatically achieves this power savings through its on-board circuitry, as no changes are required to the existing BIOS or operating system. MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins ABSOLUTE MAXIMUM RATINGS VCC ...........................................................................-0.3V to +6V V+ (Note 1) ...............................................................-0.3V to +7V V- (Note 1) ................................................................+0.3V to -7V V+ + |V-| (Note 1) .................................................................+13V Input Voltages T_IN, FORCEOFF, FORCEON ..............................-0.3V to +6V R_IN .................................................................................±25V Output Voltages T_OUT...........................................................................±13.2V R_OUT, INVALID ....................................-0.3V to (VCC + 0.3V) Short-Circuit Duration T_OUT (one at a time) ............................................Continuous Continuous Power Dissipation (TA = +70°C) 28-Pin SSOP (derate 9.52mW/°C above +70°C) .........762mW Operating Temperature Ranges MAX3238ECAI/MAX3248ECAI ...........................0°C to +70°C MAX3238EEAI/MAX3248EEAI .........................-40°C to +85°C Storage Temperature Range ............................-65°C to +150°C Lead Temperature (soldering, 10s) ................................+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 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF, and C2–C4 = 0.33µF (tested at 5.0V ±10%), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.75 6 µA 10 300 nA FORCEOFF = GND, R_IN = GND, T_IN = VCC or GND 10 300 nA FORCEON = FORCEOFF = VCC, no load 0.5 2.0 mA DC CHARACTERISTICS (VCC = +3.3V or +5.0V, TA = +25°C) Supply Current, AutoShutdown Plus Supply Current, Shutdown Supply Current, AutoShutdown Plus Disabled Receivers idle, T_IN = VCC or GND, FORCEON = GND, FORCEOFF = VCC R_IN = FORCEON = GND, FORCEOFF = VCC, T_IN = VCC or GND LOGIC INPUTS AND RECEIVER OUTPUTS MAX3238E Input Logic Threshold Low MAX3248E MAX3238E Input Logic Threshold High MAX3248E 2 T_IN (active) 0.8 1.20 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 3.3V 0.8 1.00 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 5.0V 0.8 1.45 T_IN (active) 0.6 0.7 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 3.3V 0.6 0.85 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 5.0V 0.6 1.0 V T_IN (active) 1.60 2.0 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 3.3V 1.30 2.0 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 5.0V 2.10 2.4 T_IN (active) 1.10 1.2 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 3.3V 0.95 1.2 FORCEON, FORCEOFF, and T_IN wake-up threshold; VCC = 5.0V 1.15 1.6 _______________________________________________________________________________________ V +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins (VCC = +3.0V to +5.5V, C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF, and C2–C4 = 0.33µF (tested at 5.0V ±10%), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Input Leakage Current T_IN, FORCEON, FORCEOFF (Note 2) Output Leakage Current Receivers disabled Output Voltage Low IOUT = 1.0mA Output Voltage High IOUT = -1.0mA MIN VCC 0.6 TYP MAX UNITS 9 18 µA ±0.05 ±10 µA 0.4 V VCC 0.1 V RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High -25 25 VCC = 3.3V 0.6 1.0 VCC = 5.0V 0.8 1.4 V VCC = 3.3V 1.5 2.4 VCC = 5.0V 2.0 2.4 Input Hysteresis 0.6 Input Resistance TA = +25°C 3 5 V V V 7 kΩ AutoShutdown (FORCEON = GND, FORCEOFF = VCC) 2.7 Positive threshold Receiver Input Threshold to INVALID Output High Figure 4a Receiver Input Threshold to INVALID Output Low Figure 4a INVALID Output Voltage Low IOUT = 1.0mA INVALID Output Voltage High IOUT = -1.0mA Receiver Positive or Negative Threshold to INVALID High (tINVH) VCC = 5V, Figure 4b 0.3 µs Receiver Positive or Negative Threshold to INVALID Low (tINVL) VCC = 5V, Figure 4b 60 µs Receiver or Transmitter Edge to Transmitters Enabled (tWU) VCC = 5V, Figure 4b (Note 3) 25 µs Receiver or Transmitter Edge to Shutdown (tAUTOSHDN) Figure 4b Negative threshold -2.7 -0.3 V 0.3 V 0.4 V VCC 0.6 V 15 30 60 s TRANSMITTER OUTPUTS Output Voltage Swing All transmitter outputs loaded with 3kΩ to ground ±5.0 ±5.4 V Output Resistance VCC = 0, TOUT = ±2V 300 50k Ω Output Short-Circuit Current VCC ≤ 3.6V ±35 ±60 VCC > 3.6V ±40 ±100 IEC 1000-4-2 Air-Gap Discharge Method ±15 mA ESD PROTECTION ESD Protection (R_IN, T_IN, R_OUT, T_OUT, FORCEON, FORCEOFF, INVALID, R_OUTB) IEC 1000-4-2 Contact Discharge Method ±8 Human Body Model ±15 kV _______________________________________________________________________________________ 3 MAX3238E/MAX3248E ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (VCC = +3.0V to +5.5V, C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF, and C2–C4 = 0.33µF (tested at 5.0V ±10%), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS TIMING CHARACTERISTICS Maximum Data Rate RL = 3kΩ, CL = 1000pF, one transmitter switching Receiver Propagation Delay R_IN to R_OUT, CL = 150pF Receiver Output Enable Time Normal operation 2.6 µs Receiver Output Disable Time Normal operation 2.4 µs Transmitter Skew | tPHL - tPLH | 50 ns Receiver Skew | tPHL - tPLH | 50 ns Transition-Region Slew Rate VCC = 3.3V, TA = +25°C, RL = 3kΩ to 7kΩ, measured from +3V to -3V or -3V to +3V 250 kbps tPHL 0.15 tPLH 0.15 6 CL = 150pF to 1000pF µs 30 V/µs CL = 150pF to 2500pF 4 30 Note 2: The transmitter inputs have an active positive feedback resistor. The input current goes to zero when the inputs are at the supply rails. Note 3: During AutoShutdown only, a transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic wake-up thresholds. __________________________________________Typical Operating Characteristics (VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.) MAX3238E toc02 10 SR- 8 SR+ 6 4 1 TRANSMITTER 250kbps 4 TRANSMITTERS 15.6kbps ALL TRANSMITTERS LOADED WITH 3kΩ + CL 2 VOUT1000 1500 2000 LOAD CAPACITANCE (pF) 2500 3000 250kbps 40 120kbps 30 20kbps 20 1 TRANSMITTER 20kbps, 120 kbps, 250kbps 4 TRANSMITTERS 15.6kbps ALL TRANSMITTERS LOADED WITH 3kΩ + CL 10 0 500 50 SUPPLY CURRENT (mA) FOR DATA RATES UP TO 250kbps 1 TRANSMITTER 250kbps 4 TRANSMITTERS 15.6kbps ALL TRANSMITTERS LOADED WITH 3kΩ + CL 0 4 12 SLEW RATE (V/µs) VOUT+ MAX3238E toc01 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 SUPPLY CURRENT vs. LOAD CAPACITANCE WHEN TRANSMITTING DATA SLEW RATE vs. LOAD CAPACITANCE MAX3238 TOC-03 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE TRANSMITTER OUTPUT VOLTAGE (V) MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins 0 0 500 1000 1500 2000 LOAD CAPACITANCE (pF) 2500 3000 0 500 1000 1500 2000 2500 LOAD CAPACITANCE (pF) _______________________________________________________________________________________ 3000 +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins SUPPLY CURRENT vs. SUPPLY VOLTAGE 50 40 SUPPLY CURRENT (mA) VOUT+ 1 TRANSMITTER 250kbps 4 TRANSMITTERS 15.6kbps ALL TRANSMITTERS LOADED WITH 3kΩ +1000pF MAX3238E toc05 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 MAX3238E toc04 TRANSMITTER OUTPUT VOLTAGE (V) TRANSMITTER OUTPUT VOLTAGE vs. SUPPLY VOLTAGE 30 20 1 TRANSMITTER 250kbps 4 TRANSMITTERS 15.6kbps ALL TRANSMITTERS LOADED WITH 3kΩ +1000pF 10 VOUT0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) ______________________________________________________________Pin Description PIN NAME FUNCTION 1 C2+ Positive Terminal of Inverting Charge-Pump Capacitor 2 GND Ground 3 C2- 4 V- 5, 6, 7, 10, 12 T_OUT 8, 9, 11 R_IN Negative Terminal of Inverting Charge-Pump Capacitor -5.5V Generated by the Charge Pump RS-232 Transmitter Outputs (T1OUT–T5OUT) RS-232 Receiver Inputs (R1IN–R3IN) FORCEON Force-On Input. Drive high to override AutoShutdown Plus, keeping transmitters and receivers on (FORCEOFF must be high) (Table 1). This pin has an active positive feedback resistor. Once driven to a valid logic level, the pin retains that level if left unconnected until power is cycled. 14 FORCEOFF Force-Off Input. Drive low to shut down transmitters, receivers (except R1OUTB), and onboard supply. This overrides AutoShutdown Plus and FORCEON (Table 1). This pin has an active positive feedback resistor. Once driven to a valid logic level, the pin retains that level if left unconnected until power is cycled. 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 18, 20, 21 R_OUT 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+ 13 TTL/CMOS Transmitter Inputs (T5IN–T1IN). This pin has an active positive feedback resistor. Once driven to a valid logic level, the pin retains that level if left unconnected until power is cycled. TTL/CMOS Receiver Outputs (R3OUT–R1OUT) Positive Terminal of Voltage-Doubler Charge-Pump Capacitor _______________________________________________________________________________________ 5 MAX3238E/MAX3248E Typical Operating Characteristics (continued) (VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.) MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins Table 1. Output Control Truth Table FORCEON FORCEOFF AutoShutdown Plus X 0 X 1 1 X OPERATION STATUS T_OUT R_OUT R1OUTB Shutdown (Forced Off) High-Z High-Z Active Normal Operation (Forced On) Active Active Active Active Active Active High-Z Active Active 0 1 <30s* Normal Operation (AutoShutdown Plus) 0 1 >30s* Shutdown (AutoShutdown Plus) X = Don’t care *Time since last receiver or transmitter input transition. _______________Detailed Description Dual Charge-Pump Voltage Converter The MAX3238E/MAX3248Es’ 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), 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 MAX3248E transmitters are inverting level translators that convert a logic low of 0.6V and logic high of 1.2V to 5.0V EIA/TIA-232 levels. The MAX3238E transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The MAX3238E/MAX3248E transmitters both guarantee a 250kbps data rate with worst-case loads of 3kΩ in parallel with 1000pF, 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 FORCEOFF is driven to ground, the transmitters and receivers are disabled and the outputs go high impedance, except for R1OUTB. When the AutoShutdown Plus circuitry senses that all receiver and transmitter inputs are inactive for more than 30s, the transmitters are disabled and the outputs go into a high-impedance state, but the receivers remain active. When the power is off, the MAX3238E/MAX3248E permit the outputs to be driven up to ±12V. The transmitter inputs, FORCEON and FORCEOFF, have a 400kΩ active positive-feedback resistor. Once driven to a valid logic level, they will retain this level if the driving signal is removed or goes high-impedance. Unused transmitter inputs may be left unconnected. 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 MAX3238E/MAX3248E also feature 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 monitored without forward biasing other devices connected to the receiver outputs. This is ideal for systems where VCC is set to 0 in shutdown to accommodate peripherals, such as UARTs (Figure 2). LapLink is a trademark of Traveling Software. 6 _______________________________________________________________________________________ +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins MAX3238E/MAX3248E POWER MANAGEMENT UNIT OR KEYBOARD CONTROLLER VCC FORCEOFF FORCEON INVALID PROTECTION DIODE MAX3238E/ MAX3248E PREVIOUS RS-232 VCC I Rx T1 5kΩ UART T2 Tx T3 CPU I/O CHIP WITH UART GND SHDN = GND T4 RS-232 T5 a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE RECEIVER OUTPUT IN SHUTDOWN. R1 VCC R2 TO µP R3 LOGIC TRANSITION DETECTOR I PROTECTION DIODE Figure 1. Interface Under Control of PMU AutoShutdown Plus Mode A 10nA supply current is achieved with Maxim’s AutoShutdown Plus feature, which operates when FORCEOFF is low and FORCEON is high. When the MAX3238E/MAX3248E sense no valid signal transitions on all receiver and transmitter inputs for 30s, the onboard power supply and drivers are shut off, reducing supply current to 1µA. If the receiver inputs are in the invalid range (-0.3V < R_IN < +0.3V) and the transmitter inputs are at GND or VCC, supply current is further reduced to 10nA. This occurs if the RS-232 cable is disconnected 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 transmitter 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). MAX3238E MAX3248E R1OUTB VCC Rx UART 5kΩ Tx GND R1IN R1OUT THREE-STATED T1IN T1OUT FORCEOFF = GND b) NEW MAX3238E/MAX3248E: IN SHUTDOWN, R1OUTB IS USED TO MONITOR EXTERNAL DEVICES AND R1OUT IS THREE STATED, ELIMINATING A CURRENT PATH THROUGH THE UART'S PROTECTION DIODE. Figure 2. MAX3238E/MAX3248E detect RS-232 activity when the UART and interface are shut down. _______________________________________________________________________________________ 7 MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins Table 2. INVALID Truth Table +0.3V RS-232 SIGNAL PRESENT AT ANY RECEIVER INPUT INVALID OUTPUT Yes H R_IN 60µs TIMER R -0.3V No L Tables 1 and 2 and Figure 3 summarize the MAX3238E/ MAX2348Es’ operating modes. FORCEON and FORCEOFF override the automatic circuitry and force the transceiver into its normal operating state or into its lowpower 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 devices’ charge pumps turn off, V+ decays to VCC, V- decays to ground, and the transmitter outputs are disabled (high impedance). The time required to recover from shutdown is typically 25µs (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 Plus feature so the line acts like a SHDN input. ESD Protection As with all Maxim devices, ESD protection structures are incorporated to protect against electrostatic discharges (ESDs) encountered during handling and assembly. The MAX3238E/MAX3248E RS-232 transmitters and receivers, as well as the I/O have extra protection against static electricity found in normal operation. Maxim’s engineers developed state-of-the-art structures to protect these pins against ESD of ±15kV without damage. After an ESD event, the MAX3238E/ MAX3248E keep working without latchup. ESD protection can be tested in various ways. The pins are characterized for protection to ±15kV and ±8kV (see Electrical Characteristics). ESD Test Conditions Contact Maxim for a reliability report that documents test setup, methodology, and results. 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 100pF capacitor charged to the ESD voltage of inter8 INVALID INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 60µs. Figure 3a. INVALID Functional Diagram, INVALID Low +2.7V R_IN 60µs TIMER R -2.7V INVALID INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V FOR LESS THAN 60µs. Figure 3b. INVALID Functional Diagram, INVALID High T_IN EDGE DETECT FORCEOFF S R_IN 30s TIMER EDGE DETECT AUTOSHDN R FORCEON Figure 3c. AutoShutdown Plus Logic FORCEOFF FORCEON AUTOSHDN * POWER DOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES. Figure 3d. Power-Down Logic _______________________________________________________________________________________ POWERDOWN* +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins INVALID HIGH RECEIVER INPUT LEVELS +2.7V INDETERMINATE +0.3V 0V INVALID LOW -0.3V INDETERMINATE -2.7V INVALID HIGH Figure 4a. Receiver Positive/Negative Thresholds for INVALID est, which is then discharged into the test device through a 1.5kΩ resistor. IEC 1000-4-2 The IEC 1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The MAX3238E/MAX3248E 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 testing uses a 200pF storage capacitor and zero-discharge resistance. Its objective is to mimic the stress caused by contact that occurs with handling and assembly during manufacturing. Of course, all pins (not just RS-232 inputs and outputs) require this protection during manufacturing. INVALID REGION * RECEIVER INPUTS VOLTAGE ** TRANSMITTER INPUTS VOLTAGE TRANSMITTER OUTPUTS VOLTAGE INVALID OUTPUT VCC 0 INVL tAUTOSHDN tAUTOSHDN tWU tWU V+ VCC 0 V*ALL RECEIVERS/TRANSMITTERS INACTIVE **ANY ONE RECEIVER/TRANSMITTER BECOMES ACTIVE FORCEON = GND, FORCEOFF = VCC Figure 4b. AutoShutdown Plus and INVALID Timing Diagram _______________________________________________________________________________________ 9 MAX3238E/MAX3248E help you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without additional ESD protection components. The major difference between tests done using the Human Body Model and IEC 1000-4-2 is higher peak current in IEC 1000-4-2. Because series resistance is lower in the IEC 1000-4-2 ESD test model (Figure 6a), the ESD withstand voltage measured to this standard is generally lower than that measured using the Human Body Model. Figure 6b shows the current waveform for the ±8kV IEC 1000-4-2 Level 4 ESD Contact Discharge test. RC 1MΩ CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE Cs 100pF RD 1500Ω IP 100% 90% DISCHARGE RESISTANCE STORAGE CAPACITOR DEVICE UNDER TEST Ir AMPERES 36.8% 10% 0 0 RC 50MΩ to 100MΩ CHARGE-CURRENT LIMIT RESISTOR Cs 150pF TIME tRL tDL CURRENT WAVEFORM Figure 5b. Human Body Model Current Waveform Figure 5a. Human Body ESD Test Model HIGHVOLTAGE DC SOURCE PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) RD 330Ω I 100% 90% DISCHARGE RESISTANCE STORAGE CAPACITOR DEVICE UNDER TEST IPEAK MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins 10% tr = 0.7ns to 1ns 30ns t 60ns Figure 6a. IEC 1000-4-2 ESD Test Model Therefore, the Machine Model is less relevant to the I/O ports than the Human Body Model and IEC 1000-4-2. 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 0.1µF capacitors for 3.3V operation. For other supply voltages, see Table 3 for required capacitor values. Do not use values 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 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). 10 Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform Power-Supply Decoupling In most applications, decouple VCC to ground with a 0.1µF capacitor. Further increasing this capacitor value reduces power-supply ripple and enhances noise margin. Connect the bypass capacitor as close to the IC as possible. Table 3. Required Minimum Capacitance Values VCC (V) C1, CBYPASS (µF) C2, C3, C4 (µF) 3.0 to 3.6 0.22 0.22 3.15 to 3.6 0.1 0.1 4.5 to 5.5 0.047 0.33 3.0 to 5.5 0.22 1 ______________________________________________________________________________________ +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins 5V/div T2OUT MAX3238E/MAX3248E FORCEON = FORCEOFF +5V 0 T1IN +5V 0 T1OUT 2V/div -5V T1OUT +5V R1OUT 4µs/div 0 2µs/div VCC = 3.3V, C1–C4 = 0.1µF, CLOAD = 1000pF VCC = 3.3V, C1–C4 = 0.1µF, RLOAD = 3kΩ, CLOAD = 2500pF Figure 7. Transmitter Outputs when Recovering from Shutdown or Powering Up Figure 9. Loopback Test Result at 120kbps VCC +5V 0 T1IN VCC C1+ V+ C3* C1 +5V C1T1OUT C2+ MAX3238E MAX3248E C2 0 V- -5V C4 C2+5V 0 R1OUT T_ OUT T_ IN 2µs/div VCC = 3.3V, C1–C4 = 0.1µF, CLOAD = 1000pF R_ IN R_ OUT Figure 10. Loopback Test Result at 250kbps 5kΩ FORCEON VCC FORCEOFF 1000pF GND *C3 CAN BE RETURNED TO VCC OR GND. Figure 8. Loopback Test Circuit Transmitter Outputs when Recovering from Shutdown Figure 7 shows two transmitter outputs when recovering from shutdown mode. As they become active, the out- puts are shown going to opposite RS-232 levels (one transmitter input is high, the other is low). Each transmitter is loaded with 3kΩ 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 Vexceeds approximately 3V. High Data Rates The MAX3238E/MAX3248E maintain the RS-232 ±5.0V 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 120kbps, ______________________________________________________________________________________ 11 MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins + C1 0.1µF 28 25 27 C3 0.1µF 26 TVS SUBMINIATURE CONNECTOR C5 0.1µF C1+ C2+ C1- C2- V+ MAX3238E MAX3248E ±15kV ESD PROTECTION 1 C2 0.1µF 3 V- 4 C4 0.1µF ±15kV ESD PROTECTION VCC 24 T1IN T1OUT 5 DCD 23 T2IN T2OUT 6 DSR 22 T3IN T3OUT 7 RD 19 T4IN T4OUT 10 RTS 17 T5IN T5OUT 12 TD 21 R1OUT R1IN 8 CTS 20 R2OUT R2IN 9 DTR 18 R3OUT R3IN 11 RI 16 R1OUTB 15 INVALID CONTROL GND 2 Figure 11. Data Cable Application Example 12 6 2 7 3 8 4 9 5 13 FORCEON 14 FORCEOFF 1 ______________________________________________________________________________________ +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins +3.3V 1µF 26 VCC 28 C1+ 0.1µF 0.1µF 0.1µF* MAX3238E MAX3248E V- 4 0.1µF 3 C224 T1IN T1 23 T2IN LOGIC INPUTS Data Cable Applications V+ 27 25 C11 C2+ T2 22 T3IN T3 19 T4IN T4 17 T5IN and Figure 10 shows the same test at 250kbps. For Figure 9, all transmitters were driven simultaneously at 120kbps into RS-232 loads in parallel with 1000pF. For Figure 10, a single transmitter was driven at 250kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 1000pF. T5 T1OUT 5 T2OUT 6 T3OUT 7 RS-232 OUTPUTS T4OUT 10 T5OUT 12 14 FORCEOFF AutoShutdown Plus INVALID 15 13 FORCEON The MAX3238E/MAX3248Es’ ±15kV ESD protection on both the RS-232 I/Os as well as the logic I/Os makes them ideal candidates for data cable applications. A data cable is both an electrical connection and a level translator, allowing ultra-miniaturization of cell phones and other small portable devices. Previous data cable approaches suffered from complexity due to the required protection circuits on both the logic side of the cable as well as on the RS-232 connections. The example shown in Figure 10 shows the ease of using the MAX3238E/MAX3248E in data cable applications. The MAX3238E/MAX3248Es’ five-transmitter and threereceiver configuration is optimized for a data communication equipment (DCE) application, allowing full hardware handshaking. The 9-pin RS-232 connector is configured for direct attachment to a PC’s serial port. R1OUTB is also connected to the subminiature connector. This allows the remote system to shut down until the PC asserts the ready to send (RTS) signal. R1OUTB stays active when the MAX3238E/MAX3248E is shut down (FORCEOFF = GND). 16 R1OUTB 21 R1OUT ___________________Chip Information R1IN 8 R1 TRANSISTOR COUNT: 2110 5kΩ LOGIC OUTPUTS 20 R2OUT R2IN 9 R2 RS-232 INPUTS 5kΩ 18 R3OUT R3IN 11 R3 5kΩ GND 2 *C3 MAY BE RETURNED TO EITHER VCC OR GND. ______________________________________________________________________________________ 13 MAX3238E/MAX3248E Typical Operating Circuit ________________________________________________________Package Information SSOP.EPS MAX3238E/MAX3248E +3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins 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. 14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.