19-2128; Rev 0; 8/01 +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins Features ♦ ±15kV ESD Protection on All CMOS and RS-232 Inputs and Outputs (Except INVALID) ±15kV Human Body Model ±15kV IEC 1000-4-2 Air-Gap Discharge ±8kV IEC 1000-4-2 Contact Discharge ♦ Operates Over Entire Li+ Battery Range ♦ Low Logic Threshold Down to +1.65V for Compatibility with Cell Phone Logic Supply Voltages ♦ 1µA Low-Power AutoShutdown Plus Mode ♦ Compatible with Next-Generation GSM Data Rates ♦ 20-Pin TSSOP Package Ordering Information PART 20 TSSOP 20 TSSOP 20 TSSOP MAX3381EEUP -40°C to +85°C 20 TSSOP Typical Operating Circuit C1 0.1µF C2 0.1µF TTL/CMOS INPUTS VCC VL C1+ FORCEON C5 0.1µF FORCEOFF +3.3V V+ C3 0.1µF C1C2+ MAX3380E/ MAX3381E V- C2T1IN T1OUT T2IN T2OUT C4 0.1µF RS-232 OUTPUTS VL GPS Receivers Digital Cameras R1OUT TTL/CMOS OUTPUTS AutoShutdown Plus is a trademark of Maxim Integrated Products PIN-PACKAGE 0°C to +70°C -40°C to +85°C 0°C to +70°C Applications Cell Phone Data Lump Cables PDA Data Lump Cables TEMP. RANGE MAX3380ECUP MAX3380EEUP MAX3381ECUP R1IN 5kΩ VL R2OUT RS-232 INPUTS R2IN 5kΩ Pin Configuration appears at end of data sheet. GND ________________________________________________________________ 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 MAX3380E/MAX3381E General Description The MAX3380E/MAX3381E are +2.35V to +5.5V-powered EIA/TIA-232 and V.28/V.24 communication interfaces with low power requirements, high data-rate capabilities, and enhanced electrostatic discharge (ESD) protection on both the TTL and RS-232 sides. The MAX3380E/MAX3381E have two receivers and two transmitters. All RS-232 inputs, outputs, and logic input pins are protected to ±15kV using IEC 1000-4-2 AirGap Discharge method and the Human Body Model, and ±8kV using IEC 1000-4-2 Contact Discharge method. The proprietary low-dropout transmitter output stage enables true RS-232 performance from a +3.1V to +5.5V supply with a dual charge pump. The parts reduce the transmitter output levels to RS-232-compatible levels with no increase in supply current for supplies less than +3.1V and greater than +2.35V. The +2.35V to +5.5V operating range is fully compatible with lithium-ion (Li+) batteries. The charge pump requires only four small 0.1µF capacitors for operation. The MAX3380E/MAX3381E transceivers use Maxim’s revolutionary AutoShutdown Plus™ feature to automatically enter a 1µA shutdown mode. These devices shut down the on-board power supply and drivers when they do not sense a valid signal transition for 30 seconds on either the receiver or transmitter inputs. The MAX3380E is capable of transmitting data at rates of 460kbps while maintaining RS-232 output levels, and the MAX3381E operates at data rates up to 250kbps. The MAX3381E offers a slower slew rate for applications where noise and EMI are issues. The MAX3380E/MAX3381E have a unique V L pin that allows interoperation in mixed-logic voltage systems down to +1.65V. Both input and output logic levels are referenced to the VL pin. The MAX3380E/MAX3381E are available in a space-saving TSSOP package. MAX3380E/MAX3381E +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins ABSOLUTE MAXIMUM RATINGS Short-Circuit Duration T_OUT to GND........................Continuous Continuous Power Dissipation (TA = +70°C) 20-Pin TSSOP (derate 10.9mW/°C over +70°C) .........879mW Operating Temperature Ranges MAX3380ECUP/MAX3381ECUP........................0°C to +70°C MAX3380EEUP/MAX3381EEUP .....................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C VCC to GND ...........................................................-0.3V to +6.0V VL to GND..............................................................-0.3V to +6.0V V+ to GND .............................................................-0.3V to +7.0V V- to GND ..............................................................+0.3V to -7.0V V+ + |V-| (Note 1) .................................................................+13V Input Voltages T_IN, FORCEON, FORCEOFF to GND ...............-0.3V to +6.0V R_IN to GND .....................................................................±25V Output Voltages T_OUT to GND...............................................................±13.2V R_OUT, INVALID to GND...........................-0.3V to (VL + 0.3V) Note 1: V+ and V- can have maximum magnitudes of +7V, but their absolute difference cannot 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 = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥ +4.5V, C1 = 0.047µF, C2 = C3 = C4 = 0.33µF; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25°C.) PARAMETER Supply Current, AutoShutdown Plus Supply Current, Normal Operation SYMBOL ICC CONDITIONS MIN MAX 10 FORCEOFF = GND ICC TYP Receivers idle, VT_IN = VCC or GND, FORCEON = GND, FORCEOFF = VCC FORCEON = FORCEOFF = VL, no load 1 10 0.3 1 UNITS µA mA LOGIC INPUTS (T_IN, FORCEON, FORCEOFF) Input Logic Threshold Low VIL Input Logic Threshold High VIH VCC = +5.5V, VL = +5.5V 0.4 VCC = +2.5V, VL = +1.65V 0.4 1.2 V VCC = +5.5V, VL = +5.5V VL ✕ 0.66 VCC = +2.5V, VL = +1.65V VL ✕ 0.66 Transmitter Input Hysteresis 0.5 ±0.01 Input Leakage Current V V ±1 µA 0.5 V RECEIVER OUTPUTS (R_OUT) AND INVALID Output Voltage Low IOUT = 500µA Output Voltage High IOUT = -500µA VL - 0.4 VL - 0.2 V RECEIVER INPUTS (R_IN) Input Voltage Range -25 Input Threshold Low TA = +25°C Input Threshold High TA = +25°C VL = +3.3V 0.6 1.2 VL = +5.0V 0.8 1.5 1.5 2.4 VL = +5.0V 1.8 2.4 2 0.3 TA = +25°C 3 5 _______________________________________________________________________________________ V V VL = +3.3V Input Hysteresis Input Resistance +25 V V 7 kΩ +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins (VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥ +4.5V, C1 = 0.047µF, C2 = C3 = C4 = 0.33µF; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL) Receiver Input Threshold to INVALID Output High Figure 3 Receiver Input Threshold to INVALID Output Low Figure 3 Positive threshold Negative threshold 2.7 -2.7 -0.3 0.3 V V Receiver Positive or Negative Threshold to INVALID High tINVL VCC = +5.0V, Figure 4 0.3 µs Receiver Positive or Negative Threshold to INVALID Low tINVH VCC = +5.0V, Figure 4 30 µs Receiver or Transmitter Edge to Transmitters Enabled tWU VCC = +5.0V, Figure 4 15 µs tAUTOSHDN VCC = +5.0V, Figure 4 30 s Receiver or Transmitter Edge to Transmitters Shutdown TRANSMITTER OUTPUTS VCC Mode Switch Point (VCC Falling) T_OUT = ±5.0V to ±3.7V 2.95 3.1 3.25 V VCC Mode Switch Point (VCC Rising) T_OUT = ±3.7V to ±5.5V 3.3 3.5 3.7 V VCC Mode Switch Point Hysteresis Output Voltage Swing 400 All transmitter outputs loaded with 3kΩ to ground VCC = +3.25V to +5.5V, VCC falling ±5 VCC = +2.5V to +2.95V, VCC falling ±3.7 VCC = 0, transmitter output = ±2.0V Output Resistance ±5.4 V 300 Ω 10M Output Short-Circuit Current Output Leakage Current mV VOUT = ±12V, transmitters disabled ±60 mA ±25 µA ESD PROTECTION R_IN, T_OUT, R_OUT, T_IN, FORCEON, FORCEOFF Human Body Model ±15 IEC 1000-4-2 Air-Gap Discharge Method ±15 IEC 1000-4-2 Contact Discharge Method ±8 kV _______________________________________________________________________________________ 3 MAX3380E/MAX3381E ELECTRICAL CHARACTERISTICS (continued) TIMING CHARACTERISTICS (VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥ +4.5V, C1 = 0.047µF, C2 = C3 = C4 = 0.33µF; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN RL = 3kΩ, CL = 1000pF, one transmitter switching Maximum Data Rate tPLH Receiver Propagation Delay MAX3381E 250 MAX3380E 460 MAX UNITS kbps 0.15 Receiver input to receiver output, CL = 100pF tPHL TYP µs 0.15 Transmitter Skew tPHL- tPLH (Note 2) 200 ns Receiver Skew tPHL- tPLH 50 ns Transition Region Slew Rate (MAX3380E) VCC = +4.2V, -3.0V < T_OUT< +3.0V, RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C 20 100 V/µs Transition Region Slew Rate (MAX3381E) VCC = +4.2V, -3.0V < T_OUT< +3.0V, RL = 3kΩ, CL = 150pF to 1000pF, TA = +25°C 6 30 V/µs Transition Region Slew Rate (MAX3380E) VCC = +2.35V, -3.0V < T_OUT< +3.0V, RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C 30 V/µs Transition Region Slew Rate (MAX3381E) VCC = +2.35V, -3.0V < T_OUT< +3.0V, RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C 10 V/µs Note 2: Transmitter skew is measured at the transmitter zero crosspoint. Typical Operating Characteristics (VCC = VL = +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL = 3kΩ, CL = 1000pF, data rate is 250kbps, TA = +25°C, unless otherwise noted.) TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE 4 2 0 -2 -4 VOUT-6 500 1000 1500 2000 LOAD CAPACITANCE (pF) 2500 3000 35 30 4 2 0 -2 25 VCC = +4.2V 20 15 10 VOUT- -4 MAX3380E toc03 VOUT+ VCC = +2.5V 5 -6 0 4 6 40 SLEW RATE (V/µs) VOUT+ VCC = +2.5V MAX3380E SLEW RATE vs. LOAD CAPACITANCE MAX3380E toc02 6 8 TRANSMITTER OUTPUT VOLTAGE (V) VCC = +4.2V TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE MAX3380E toc01 8 TRANSMITTER OUTPUT VOLTAGE (V) MAX3380E/MAX3381E +2.35V to +5.5V, 1µA, 2Tx/2Rx 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 LOAD CAPACITANCE (pF) _______________________________________________________________________________________ 2500 3000 +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins SUPPLY CURRENT (mA) VCC = +4.2V 11 10 VCC = +2.5V 60 50 30 8 20 7 10 6 250kbps 40 20kbps 500 1000 1500 2000 2500 3000 0 500 LOAD CAPACITANCE (pF) 1000 1500 2000 2500 2 0 -2 VOUT- -4 3000 2.5 3.5 4.5 SUPPLY VOLTAGE (V) 25 1 TRANSMITTER SWITCHING 20 SUPPLY CURRENT (mA) VOUT+ 5.5 SUPPLY CURRENT vs. SUPPLY VOLTAGE (VCC FALLING) MAX3380E toc07 TRANSMITTER OUTPUT VOLTAGE (V) 8 4 2 0 -2 15 10 5 VOUT- -4 VOUT+ 4 LOAD CAPACITANCE (pF) TRANSMITTER OUTPUT VOLTAGE vs. SUPPLY VOLTAGE (VCC RISING) 6 6 -6 0 0 8 MAX3380E toc08 9 460kbps TRANSMITTER OUTPUT VOLTAGE vs. SUPPLY VOLTAGE (VCC FALLING) TRANSMITTER OUTPUT VOLTAGE (V) 12 1 TRANSMITTER SWITCHING 70 MAX3381E toc05 13 SLEW RATE (V/µs) 80 MAX3380E toc04 14 SUPPLY CURRENT vs. LOAD CAPACITANCE WHEN TRANSMITTING DATA MAX3380E toc06 MAX3381E SLEW RATE vs. LOAD CAPACITANCE 0 -6 2.5 3.5 4.5 SUPPLY VOLTAGE (V) 2.5 5.5 3.5 4.5 MAX3380E DATASTREAM VCC = +4.2V MAX3380E DATASTREAM VCC = +2.5V MAX3380E toc09 MAX3380E toc10 5V 5V T_IN 5V/div 0 T_IN 5V/div 0 5V T_OUT 5V/div 5.5 SUPPLY VOLTAGE (V) 0 5V T_OUT 5V/div 0 -5V -5V VCC = VL = +2.5V 1µs/div 1µs/div _______________________________________________________________________________________ 5 MAX3380E/MAX3381E Typical Operating Characteristics (continued) (VCC = VL = +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL = 3kΩ, CL = 1000pF, data rate is 250kbps, TA = +25°C, unless otherwise noted.) +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E Pin Description PIN NAME 1 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor — 2 V+ +5.5V/+4.0V Generated by the Charge Pump — 3 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor — 4 C2+ Positive Terminal of Inverting Charge-Pump Capacitor — 5 C2- Negative Terminal of Inverting Charge-Pump Capacitor — 6 V- 7 INVALID 8, 9 T_IN 10, 11 R_OUT 12 FORCEON 13 VL 14, 15 R_IN 16, 17 T_OUT 18 GND 19 FORCEOFF 20 VCC -5.5V/-4.0V Generated by the Charge Pump — INVALID is asserted if any inputs of the receivers are in an invalid state; -0.3V < VR_IN < +0.3V — TTL/CMOS Transmitter Inputs Referenced to VL (T1IN, T2IN) ✔ TTL/CMOS Receiver Outputs Referenced to VL (R2OUT, R1OUT) ✔ Force-On Input. Drive high to override automatic circuitry keeping transmitters on (FORCEOFF must be high) (Table 1). ✔ Logic Level Supply. +1.65V to +5.5V, sets CMOS logic thresholds and CMOS outputs. — RS-232 Receiver Inputs (R2IN, R1IN) ✔ RS-232 Transmitter Outputs (T2OUT, T1OUT) ✔ Ground — Force-Off Input. Drive low to shut down transmitters and on-board power supply. This overrides all automatic circuitry and FORCEON (Table 1). ✔ +2.35V to +5.5V Supply Voltage — Detailed Description The MAX3380E/MAX3381E are RS-232 transceivers that maximize battery life by reducing current consumption at low battery levels. When the supply voltage is above +3.7V, the RS-232 outputs are at ±5.5V, which is compliant with the RS-232 standard. As the supply voltage drops below the +3.1V set point, the RS-232 outputs change to ±3.7V, which is compatible with the RS-232 standard. The outputs will remain at the compatible levels until the supply voltage rises above +3.5V, where they return to compliant levels. 400mV of hysteresis protects against power-supply bounce that may cause numerous mode changes. Most devices that use charge pumps to double and invert voltages consume higher current when the supply voltage is less than half of the required output voltage. This is due to the fact that the charge pump is constantly operating because the output voltage is below the regulation voltage. This requires more supply current because the output will never reach the regulation voltage and switch off. The MAX3380E/MAX3381E reduce 6 ESD PROTECTED FUNCTION the output voltage requirement allowing the charge pump to operate with supply voltages down to +2.35V. Dual-Mode Regulated Charge-Pump Voltage Converter The MAX3380E/MAX3381Es’ internal power supply is a dual-mode regulated charge pump. The output regulation point depends on VCC and the direction in which VCC moves through the switchover region of +2.95V < VCC < +3.7V. For supply voltages above +3.7V, the charge pump will generate +5.5V at V+ and -5.5V at V-. 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. For supply voltages below +2.95V, the charge pump will generate +4.0V at V+ and -4.0V at V-. The charge pumps operate in a discontinuous mode. Each charge pump requires a flying capacitor (C1, C2) and a reservoir capacitor (C3, C4) to generate the V+ and V- supplies (see Typical Operating Circuit). _______________________________________________________________________________________ +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins The MAX3380E/MAX3381E include a switchover circuit between RS-232-compliant and RS-232-compatible modes that has approximately 400mV of hysteresis around the switchover point. The hysteresis is shown in Figure 1. This large hysteresis helps to avoid mode change under battery or power-supply bounce. Under a decaying VCC, the charge pump will generate an output voltage of ±5.5V with a V CC input range between +3.1V and +5.5V. When VCC drops below the switchover point of +3.1V, the charge pump switches into RS-232-compatible mode generating ±4V. When VCC is rising, the charge pump will generate an output voltage of ±4.0V, while VCC is between +2.5V and +3.5V. When VCC rises above the switchover voltage of +3.5V, the charge pump switches to RS-232compliant mode to generate an output voltage of ±5.5V. RS-232 Transmitters The transmitters are inverting level translators that convert CMOS-logic levels to RS-232-compatible levels. The MAX3380E/MAX3381E will automatically reduce the RS-232-compliant levels from ±5.5V to ±3.7V when VCC falls below approximately +3.1V. The reduced levels are RS-232-compatible and reduce supply current requirements that help preserve the battery. Built-in hysteresis of approximately 400mV for VCC ensures that the RS-232 output levels do not change if VCC is noisy or has a sudden current draw causing the supply voltage to drop slightly. The outputs will return to RS232-compliant levels (±5.5V) when VCC rises above approximately +3.5V. +4.5V VCC 2V/div +2.5V +5.8V V+ 2V/div +4.4V 20ms/div Figure 1. V+ Switchover for Changing Vcc The MAX3380E/MAX3381E transmitters guarantee a data rate of 460kbps/250kbps, respectively, with worst-case loads of 3kΩ in parallel with 1000pF. Transmitters can be paralleled to drive multiple receivers. When FORCEOFF is driven to ground, the transmitters are disabled and the outputs go into high impedance; receivers remain active. 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, and the receivers remain active. When the power is off, the MAX3380E/MAX3381E permit the outputs to be driven up to ±12V. The transmitter inputs have a 400kΩ active positive feedback resistor. They will retain a valid logic level if the driving signal is removed or goes high impedance. Connect unused transmitter inputs to VCC or ground. RS-232 Receivers The receivers convert RS-232 signals to logic levels referred to VL. Both receivers are active in shutdown (Table 1). AutoShutdown Plus Mode The MAX3380E/MAX3381E achieve a 1µA supply current with Maxim’s AutoShutdown Plus feature, which operates when FORCEOFF is high and FORCEON is low. When these devices do not sense a valid signal transition on any receiver and transmitter input for 30s, 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 if the UART driving the transmitter inputs is inactive. 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. Figures 2a and 2b show valid and invalid RS-232 receiver voltage levels. INVALID indicates the receiver input’s condition, and is independent of the FORCEON and FORCEOFF states. Figure 2 and Table 1 summarize the MAX3380E/MAX3381E’s operating modes. FORCEON and FORCEOFF 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. By connecting FORCEON to INVALID, the MAX3380E/ MAX3381E is shut down when no valid receiver level and no receiver or transmitter edge is detected for 30s, and wakes up when a receiver or transmitter edge is detected (Figure 2c). _______________________________________________________________________________________ 7 MAX3380E/MAX3381E Voltage Generation in the Switchover Region MAX3380E/MAX3381E +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins Table 1. AutoShutdown Plus Truth Table FORCEON FORCEOFF VALID RECEIVER LEVEL RECEIVER OR TRANSMITTER EDGE WITHIN 30s T_OUT R_OUT Shutdown (Forced Off) X 0 X X High-Z Active Normal Operation (Forced On) 1 1 X X Active Active Normal Operation (AutoShutdown Plus) 0 1 X Yes Active Active Shutdown (AutoShutdown Plus) 0 1 X No High-Z Active Normal Operation INVALID 1 Yes X Active Active Normal Operation INVALID 1 X Yes Active Active Shutdown INVALID 1 No No High-Z Active Normal Operation (AutoShutdown) INVALID INVALID Yes X Active Active Shutdown (AutoShutdown) INVALID INVALID No X High-Z Active OPERATION STATUS X = Don’t care +2.7V +0.3V R_IN -0.3V R_IN 30µs TIMER R INVALID INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs. Figure 2a. INVALID Functional Diagram, INVALID Low 8 -2.7V 0.3µs TIMER R INVALID INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V FOR LESS THAN 30µs. Figure 2b. INVALID Functional Diagram, INVALID High _______________________________________________________________________________________ +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins S 30s TIMER EDGE DETECT R_IN FORCEOFF FORCEOFF POWERDOWN* FORCEON AUTOSHDN AUTOSHDN R * POWERDOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES. FORCEON Figure 2c. AutoShutdown Plus Logic Figure 2d. Power-Down Logic TRANSMITTERS ENABLED, INVALID HIGH By connecting FORCEON and FORCEOFF to INVALID, the MAX3380E/MAX3381E are shut down when no valid receiver level is detected. +2.7V INDETERMINATE +0.3V AutoShutdown, TRANSMITTERS DISABLED, 1µA SUPPLY CURRENT INVALID LOW 0 -0.3V INDETERMINATE -2.7V TRANSMITTERS ENABLED, INVALID HIGH VL Logic Supply Input Unlike other RS-232 interface devices where the receiver outputs swing between 0 and VCC, the MAX3380E/ MAX3381E feature a separate logic supply input (VL) that sets VOH for the receiver and INVALID outputs. VL also sets the threshold for the transmitter inputs, FORCEON and FORCEOFF. This feature allows a great deal of flexibility in interfacing to many different types of systems with different logic levels. Connect this input to Figure 3. AutoShutdown Trip Levels RECEIVER INPUTS INVALID } REGION TRANSMITTER INPUTS TRANSMITTER OUTPUTS INVALID OUTPUT VL 0 tINVL tINVH tAUTOSHDN tAUTOSHDN tWU tWU V+ VCC 0 V- Figure 4. AutoShutdown Plus/INVALID Timing Diagram _______________________________________________________________________________________ 9 MAX3380E/MAX3381E EDGE DETECT T_IN RC 1MΩ CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE Cs 100pF RD 1500Ω RC 50MΩ to 100MΩ DISCHARGE RESISTANCE CHARGE-CURRENT LIMIT RESISTOR DEVICE UNDER TEST STORAGE CAPACITOR Figure 5a. Human Body ESD Test Model IP 100% 90% Ir HIGHVOLTAGE DC SOURCE Cs 150pF RD 330Ω DISCHARGE RESISTANCE STORAGE CAPACITOR DEVICE UNDER TEST Figure 6a. IEC 1000-4-2 ESD Test Model I 100% 90% PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) IPEAK MAX3380E/MAX3381E +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins AMPERES 36.8% 10% 10% 0 0 tRL TIME tDL CURRENT WAVEFORM Figure 5b. Human Body Current Waveform the host logic supply (+1.65V to +5.5V). The VL input will draw a maximum current of 20µA with receiver outputs unloaded. ±15kV ESD Protection Maxim has developed state-of-the-art structures to protect these pins against an ESD of ±15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and power-down. After an ESD event, Maxim’s “E” version devices keep working without latch-up, whereas competing RS-232 products can latch and must be powered down to remove latchup. ESD protection can be tested in various ways. The transmitter and receiver outputs and receiver and logic inputs of this product family are characterized for protection to the following limits: • ±15kV using the Human Body Model • ±8kV using the Contact Discharge method specified in IEC 1000-4-2 • ±15kV using IEC 1000-4-2’s Air-Gap Discharge method 10 tr = 0.7ns to 1ns 30ns t 60ns Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform ESD Test Conditions ESD performance depends on a variety of 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 interest, 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 ICs. The MAX3380E/MAX3381E help you design equipment that meets Level 4, the highest level of IEC 1000-4-2 without the need for additional ESDprotection 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 model. Hence, the ESD withstand voltages measured ______________________________________________________________________________________ +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins Machine Model The Machine Model for ESD tests all pins using a 200pF storage capacitor and zero discharge resistance. Its objective is to emulate the stress caused by contact that occurs with handling and assembly during manufacturing. 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 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 2 for required capacitor values. Do not use values smaller than those listed in Table 2. 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 C5 to maintain the proper ratios (C1 to the other capacitors). When using the minimum required capacitor values, make sure the capacitor value does not degrade excessively with temperature. If in doubt, use capacitors with a large nominal value. The capacitor’s equivalent series resistance (ESR) usually rises at low temperatures and influences the amount of ripple on V+ and V-. Power-Supply Decoupling In most circumstances, connect a 0.1µF capacitor from VCC to GND. This capacitor is for noise reduction. If the MAX3380E/MAX3381E are used in a data cable application, add a 47µF capacitor from VCC to ground. The 47µF capacitor is used to ensure that the current needed during power-up is supplied to the device. In applications that are sensitive to power-supply noise, decouple VCC to ground with a capacitor of the same value as charge-pump capacitor C1. Connect bypass capacitors as close to the IC as possible. Transmitter Outputs when Recovering from 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). Each transmitter is loaded with 3kΩ in parallel with 1000pF. 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 MAX3380E/MAX3381E 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 for the MAX3380E at 460kbps with true RS-232 output voltage levels (VCC = +4.2V). Figure 10 shows the same test with RS-232-compatible levels (V CC = +2.5V). With data rates as high as 460kbps, the MAX3380E is compatible with 2.5-Generation GSM standards. 5V/div 5V FORCEON = 0 FORCEOFF 6V T2OUT 2V/div 0 Table 2. Minimum Required Capacitor Values VCC (V) C1, C5 (µF) C2, C3, C4 (µF) +2.35 to +3.6 0.1 0.1 +4.5 to +5.5 0.047 0.33 +2.35 to +5.5 0.22 1 T1OUT 6V 4µs/div VCC = 3.3V, C1–C4 = 0.1µF, CLOAD = 1000pF Figure 7. Transmitter Outputs when Recovering from Shutdown or Powering Up ______________________________________________________________________________________ 11 MAX3380E/MAX3381E to IEC 1000-4-2 are generally lower than that measured using the Human Body Model. Figure 6a shows the IEC 1000-4-2 model, and Figure 6b shows the current waveform for the ±8kV IEC 1000-4-2 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. MAX3380E/MAX3381E +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins For Figure 9 and Figure 10, a single transmitter was driven at 460kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 1000pF. Data Cable Applications The MAX3380E/MAX3381Es’ ±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 11 shows the ease of using the MAX3380E/MAX3381E in data cable applications. For best performance, keep the logic level lines short and use the RS-232 level lines to span any distance. 5V T1IN 5V/div 0 5V T1OUT 5V/div 0 -5V 5V R1OUT 5V/div 0 1µs/div VCC = VL = +4.2V, C1 = 0.1µF, C2 = C3 = C4 = 1µF, CLOAD = 1000pF Figure 9. Loopback Test Results at 460kbps (VCC = +4.2V) VCC C5 VCC C1+ 5V V+ C1 C1- C2 0 VL C3 C2+ 2V T1IN 2V/div MAX3380E MAX3381E VC4 C2- 0 -5V 2V R1OUT 2V/div 0 TIME (1µs/div) T_ OUT T_ IN T1OUT 5V/div VCC = VL = +2.5V, C1 = 0.1µF, C2 = C3 = C4 = 1µF, CLOAD = 1000pF R_ IN R_ OUT 5kΩ FORCEON VCC FORCEOFF Figure 10. Loopback Test Results at 460kbps (VCC = +2.5V) 1000pF GND Figure 8. Loopback Test Circuit 12 ______________________________________________________________________________________ +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E 47µF 0.1µF VCC VL FORCEOFF 0.1µF FORCEON V+ C1+ 0.1µF C10.1µF V- C2+ 0.1µF C2- VBATT MAX3380E/ MAX3381E CELL PHONE LOGIC LEVELS PERIPHERALS RS-232 LEVELS Tx T1IN T1OUT Tx RTS T2IN T2OUT CTS Rx R1OUT R1IN Rx CTS R2OUT R2IN RTS I/O INVALID Figure 11. Typical Application Circuit Pin Configuration Chip Information TRANSISTOR COUNT: 1467 PROCESS: BiCMOS TOP VIEW 20 VCC C1+ 1 V+ 2 19 FORCEOFF C1- 3 18 GND C2+ 4 C2- 5 V- 6 17 T1OUT MAX3380E/ MAX3381E INVALID 7 16 T2OUT 15 R1IN 14 R2IN T1IN 8 13 VL T2IN 9 12 FORCEON R2OUT 10 11 R1OUT TSSOP ______________________________________________________________________________________ 13 MAX3380E/MAX3381E +2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers with ±15kV ESD-Protected I/O and Logic Pins TSSOP.EPS Package Information 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.