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19-2128; Rev 0; 8/01
+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins
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 0.1F capacitors for operation. The MAX3380E/MAX3381E transceivers use Maxim's revolutionary AutoShutdown PlusTM feature to automatically enter a 1A 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.
Features
o 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 o Operates Over Entire Li+ Battery Range o Low Logic Threshold Down to +1.65V for Compatibility with Cell Phone Logic Supply Voltages o 1A Low-Power AutoShutdown Plus Mode o Compatible with Next-Generation GSM Data Rates o 20-Pin TSSOP Package
MAX3380E/MAX3381E
Ordering Information
PART MAX3380ECUP MAX3380EEUP MAX3381ECUP MAX3381EEUP TEMP. RANGE 0C to +70C -40C to +85C 0C to +70C -40C to +85C PIN-PACKAGE 20 TSSOP 20 TSSOP 20 TSSOP 20 TSSOP
Typical Operating Circuit
+3.3V C5 0.1F
VCC C1+ C1C2+ C2T1IN
VL
C1 0.1F
FORCEOFF
FORCEON V+
C2 0.1F
MAX3380E/ MAX3381E
C3 0.1F VC4 0.1F
Applications
Cell Phone Data Lump Cables PDA Data Lump Cables GPS Receivers Digital Cameras
TTL/CMOS OUTPUTS TTL/CMOS INPUTS
T1OUT RS-232 OUTPUTS
T2IN VL R1OUT
T2OUT
R1IN 5k VL RS-232 INPUTS
AutoShutdown Plus is a trademark of Maxim Integrated Products Pin Configuration appears at end of data sheet.
R2OUT
R2IN 5k GND
________________________________________________________________ Maxim Integrated Products
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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.
+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
ABSOLUTE MAXIMUM RATINGS
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) Short-Circuit Duration T_OUT to GND........................Continuous Continuous Power Dissipation (TA = +70C) 20-Pin TSSOP (derate 10.9mW/C over +70C) .........879mW Operating Temperature Ranges MAX3380ECUP/MAX3381ECUP........................0C to +70C MAX3380EEUP/MAX3381EEUP .....................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = 0.1F; when VCC +4.5V, C1 = 0.047F, C2 = C3 = C4 = 0.33F; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25C.)
PARAMETER Supply Current, AutoShutdown Plus Supply Current, Normal Operation SYMBOL ICC CONDITIONS Receivers idle, VT_IN = VCC or GND, FORCEON = GND, FORCEOFF = VCC FORCEOFF = GND ICC FORCEON = FORCEOFF = VL, no load 1 0.3 MIN TYP MAX 10 10 1 mA UNITS A
LOGIC INPUTS (T_IN, FORCEON, FORCEOFF) Input Logic Threshold Low Input Logic Threshold High Transmitter Input Hysteresis Input Leakage Current RECEIVER OUTPUTS (R_OUT) AND INVALID Output Voltage Low Output Voltage High RECEIVER INPUTS (R_IN) Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance TA = +25C 3 TA = +25C TA = +25C VL = +3.3V VL = +5.0V VL = +3.3V VL = +5.0V -25 0.6 0.8 1.2 1.5 1.5 1.8 0.3 5 7 2.4 2.4 +25 V V V V k IOUT = 500A IOUT = -500A VL - 0.4 VL - 0.2 0.5 V V VIL VIH VCC = +5.5V, VL = +5.5V VCC = +2.5V, VL = +1.65V VCC = +5.5V, VL = +5.5V VCC = +2.5V, VL = +1.65V 0.5 0.01 1 0.4 0.4 VL 0.66 VL 0.66 1.2 V V V A
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1F; when VCC +4.5V, C1 = 0.047F, C2 = C3 = C4 = 0.33F; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25C.)
PARAMETER Receiver Input Threshold to INVALID Output High Receiver Input Threshold to INVALID Output Low Receiver Positive or Negative Threshold to INVALID High Receiver Positive or Negative Threshold to INVALID Low Receiver or Transmitter Edge to Transmitters Enabled Receiver or Transmitter Edge to Transmitters Shutdown TRANSMITTER OUTPUTS VCC Mode Switch Point (VCC Falling) VCC Mode Switch Point (VCC Rising) VCC Mode Switch Point Hysteresis All transmitter outputs loaded with 3k to ground VCC = +3.25V to +5.5V, VCC falling VCC = +2.5V to +2.95V, VCC falling 5 3.7 300 10M 60 VOUT = 12V, transmitters disabled Human Body Model R_IN, T_OUT, R_OUT, T_IN, FORCEON, FORCEOFF IEC 1000-4-2 Air-Gap Discharge Method IEC 1000-4-2 Contact Discharge Method 15 15 8 kV 25 mA A T_OUT = 5.0V to 3.7V T_OUT = 3.7V to 5.5V 2.95 3.3 3.1 3.5 400 5.4 V 3.25 3.7 V V mV tINVL tINVH tWU SYMBOL CONDITIONS Positive threshold Negative threshold -2.7 -0.3 0.3 30 15 30 0.3 MIN TYP MAX 2.7 UNITS
MAX3380E/MAX3381E
AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL) Figure 3 Figure 3 VCC = +5.0V, Figure 4 VCC = +5.0V, Figure 4 VCC = +5.0V, Figure 4 V V s s s s
tAUTOSHDN VCC = +5.0V, Figure 4
Output Voltage Swing
Output Resistance Output Short-Circuit Current Output Leakage Current ESD PROTECTION
VCC = 0, transmitter output = 2.0V
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
TIMING CHARACTERISTICS
(VCC = +2.35V to +5.5V, VL = +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1F; when VCC +4.5V, C1 = 0.047F, C2 = C3 = C4 = 0.33F; TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25C.)
PARAMETER Maximum Data Rate Receiver Propagation Delay Transmitter Skew Receiver Skew Transition Region Slew Rate (MAX3380E) Transition Region Slew Rate (MAX3381E) Transition Region Slew Rate (MAX3380E) Transition Region Slew Rate (MAX3381E) tPLH tPHL tPHL- tPLH VCC = +4.2V, -3.0V < T_OUT< +3.0V, RL = 3k, CL = 250pF to 1000pF, TA = +25C VCC = +4.2V, -3.0V < T_OUT< +3.0V, RL = 3k, CL = 150pF to 1000pF, TA = +25C VCC = +2.35V, -3.0V < T_OUT< +3.0V, RL = 3k, CL = 250pF to 1000pF, TA = +25C VCC = +2.35V, -3.0V < T_OUT< +3.0V, RL = 3k, CL = 250pF to 1000pF, TA = +25C 20 6 30 10 SYMBOL CONDITIONS RL = 3k, CL = 1000pF, one transmitter switching MAX3381E MAX3380E MIN 250 460 0.15 0.15 200 50 100 30 TYP MAX UNITS kbps s ns ns V/s V/s V/s V/s
Receiver input to receiver output, CL = 100pF
tPHL- tPLH (Note 2)
Note 2: Transmitter skew is measured at the transmitter zero crosspoint.
Typical Operating Characteristics
(VCC = VL = +4.2V, C1 = 0.22F, C2 = C3 = C4 = 1F, C5 = 0.1F parallel with 47F, RL = 3k, CL = 1000pF, data rate is 250kbps, TA = +25C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX3380E toc01
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX3380E toc02
MAX3380E SLEW RATE vs. LOAD CAPACITANCE
35 30 SLEW RATE (V/s) 25 20 15 10 5 0 VCC = +2.5V VCC = +4.2V
MAX3380E toc03
8 VCC = +4.2V TRANSMITTER OUTPUT VOLTAGE (V) 6 4 2 0 -2 -4 VOUT-6 0 500 1000 1500 2000 2500 VOUT+
8 VCC = +2.5V TRANSMITTER OUTPUT VOLTAGE (V) 6 VOUT+ 4 2 0 -2 -4 -6 VOUT-
40
3000
0
500
1000
1500
2000
2500
3000
0
500
1000
1500
2000
2500
3000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins
Typical Operating Characteristics (continued)
(VCC = VL = +4.2V, C1 = 0.22F, C2 = C3 = C4 = 1F, C5 = 0.1F parallel with 47F, RL = 3k, CL = 1000pF, data rate is 250kbps, TA = +25C, unless otherwise noted.)
MAX3381E SLEW RATE vs. LOAD CAPACITANCE
MAX3380E toc04
MAX3380E/MAX3381E
SUPPLY CURRENT vs. LOAD CAPACITANCE WHEN TRANSMITTING DATA
MAX3381E toc05
TRANSMITTER OUTPUT VOLTAGE vs. SUPPLY VOLTAGE (VCC FALLING)
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3380E toc06
14 13 12 SLEW RATE (V/s) 11 10 9 8 7 6 0 500 1000 1500 2000 2500 VCC = +2.5V VCC = +4.2V
80 1 TRANSMITTER SWITCHING 70 SUPPLY CURRENT (mA) 60 50 40 30 20 10 0 20kbps 250kbps 460kbps
8 6 4 2 0 -2 -4 -6 VOUTVOUT+
3000
0
500
1000
1500
2000
2500
3000
2.5
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
3.5 4.5 SUPPLY VOLTAGE (V)
5.5
TRANSMITTER OUTPUT VOLTAGE vs. SUPPLY VOLTAGE (VCC RISING)
MAX3380E toc07
SUPPLY CURRENT vs. SUPPLY VOLTAGE (VCC FALLING)
1 TRANSMITTER SWITCHING 20 SUPPLY CURRENT (mA)
MAX3380E toc08
8 TRANSMITTER OUTPUT VOLTAGE (V) 6 4 2 0 -2 -4 -6 2.5 3.5 4.5 SUPPLY VOLTAGE (V) VOUTVOUT+
25
15
10
5
0 5.5 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V)
MAX3380E DATASTREAM VCC = +4.2V
MAX3380E toc09
MAX3380E DATASTREAM VCC = +2.5V
MAX3380E toc10
T_IN 5V/div
5V 0 T_IN 5V/div
5V 0
5V T_OUT 5V/div 0 -5V VCC = VL = +2.5V 1s/div 1s/div T_OUT 5V/div
5V 0 -5V
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
Pin Description
PIN 1 2 3 4 5 6 7 8, 9 10, 11 12 13 14, 15 16, 17 18 19 20 NAME C1+ V+ C1C2+ C2VINVALID T_IN R_OUT FORCEON VL R_IN T_OUT GND FORCEOFF VCC FUNCTION Positive Terminal of Voltage-Doubler Charge-Pump Capacitor +5.5V/+4.0V Generated by the Charge Pump Negative Terminal of Voltage-Doubler Charge-Pump Capacitor Positive Terminal of Inverting Charge-Pump Capacitor Negative Terminal of Inverting Charge-Pump Capacitor -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 ESD PROTECTED -- -- -- -- -- -- -- -- -- --
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
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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).
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins
Voltage Generation in the Switchover Region
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. The MAX3380E/MAX3381E transmitters guarantee a data rate of 460kbps/250kbps, respectively, with worst-case loads of 3k 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 400k 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.
MAX3380E/MAX3381E
RS-232 Receivers
The receivers convert RS-232 signals to logic levels referred to VL. Both receivers are active in shutdown (Table 1).
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.
AutoShutdown Plus Mode
The MAX3380E/MAX3381E achieve a 1A 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 1A. 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).
VCC 2V/div
+4.5V +2.5V
V+ 2V/div
+5.8V +4.4V
20ms/div
Figure 1. V+ Switchover for Changing Vcc
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
Table 1. AutoShutdown Plus Truth Table
OPERATION STATUS Shutdown (Forced Off) Normal Operation (Forced On) Normal Operation (AutoShutdown Plus) Shutdown (AutoShutdown Plus) Normal Operation Normal Operation Shutdown Normal Operation (AutoShutdown) Shutdown (AutoShutdown) FORCEON FORCEOFF VALID RECEIVER LEVEL X RECEIVER OR TRANSMITTER EDGE WITHIN 30s X T_OUT R_OUT
X
0
High-Z
Active
1
1
X
X
Active
Active
0
1
X
Yes
Active
Active
0 INVALID INVALID INVALID INVALID INVALID
1 1 1 1 INVALID INVALID
X Yes X No Yes No
No X Yes No X X
High-Z Active Active High-Z Active High-Z
Active Active Active Active Active Active
X = Don't care
+0.3V
+2.7V
R_IN
R_IN 30s TIMER R INVALID -2.7V
-0.3V
0.3s TIMER R
INVALID
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30s.
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V FOR LESS THAN 30s.
Figure 2a. INVALID Functional Diagram, INVALID Low
Figure 2b. INVALID Functional Diagram, INVALID High
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
T_IN EDGE DETECT FORCEOFF S 30s TIMER R
* POWERDOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES. FORCEOFF POWERDOWN*
AUTOSHDN
FORCEON AUTOSHDN
R_IN
EDGE DETECT
FORCEON
Figure 2c. AutoShutdown Plus Logic
Figure 2d. Power-Down Logic
TRANSMITTERS ENABLED, INVALID HIGH +2.7V INDETERMINATE +0.3V 0 -0.3V -2.7V TRANSMITTERS ENABLED, INVALID HIGH AutoShutdown, TRANSMITTERS DISABLED, 1A SUPPLY CURRENT INVALID LOW INDETERMINATE
By connecting FORCEON and FORCEOFF to INVALID, the MAX3380E/MAX3381E are shut down when no valid receiver level is detected.
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
} REGION
INVALID
TRANSMITTER INPUTS
TRANSMITTER OUTPUTS VL 0
INVALID OUTPUT
tINVL
tINVH tAUTOSHDN tWU
tAUTOSHDN tWU
V+ VCC 0 V-
Figure 4. AutoShutdown Plus/INVALID Timing Diagram _______________________________________________________________________________________ 9
+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE RD 1500 DISCHARGE RESISTANCE DEVICE UNDER TEST HIGHVOLTAGE DC SOURCE RC 50M to 100M CHARGE-CURRENT LIMIT RESISTOR RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
Cs 100pF
STORAGE CAPACITOR
Cs 150pF
STORAGE CAPACITOR
Figure 5a. Human Body ESD Test Model
Figure 6a. IEC 1000-4-2 ESD Test Model
I 100% 90% IPEAK
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
10% tr = 0.7ns to 1ns 30ns 60ns t
tDL CURRENT WAVEFORM
Figure 5b. Human Body Current Waveform
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
the host logic supply (+1.65V to +5.5V). The VL input will draw a maximum current of 20A with receiver outputs unloaded.
ESD Test Conditions
ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, methodology, and results.
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
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 1.5k 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
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+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins
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.
Power-Supply Decoupling
In most circumstances, connect a 0.1F capacitor from VCC to GND. This capacitor is for noise reduction. If the MAX3380E/MAX3381E are used in a data cable application, add a 47F capacitor from VCC to ground. The 47F 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.
MAX3380E/MAX3381E
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.
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 3k 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.
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 0.1F 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-.
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 FORCEON = 0 FORCEOFF 6V T2OUT
5V/div
2V/div
0
Table 2. Minimum Required Capacitor Values
VCC (V) +2.35 to +3.6 +4.5 to +5.5 +2.35 to +5.5 C1, C5 (F) 0.1 0.047 0.22 C2, C3, C4 (F) 0.1 0.33 1
4s/div VCC = 3.3V, C1-C4 = 0.1F, CLOAD = 1000pF
T1OUT 6V
Figure 7. Transmitter Outputs when Recovering from Shutdown or Powering Up
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11
+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
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.
T1IN 5V/div
5V 0 5V
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.
VCC C5
T1OUT 5V/div
0 -5V 5V 0
R1OUT 5V/div
1s/div VCC = VL = +4.2V, C1 = 0.1F, C2 = C3 = C4 = 1F, CLOAD = 1000pF
Figure 9. Loopback Test Results at 460kbps (VCC = +4.2V)
T1IN 2V/div
2V 0 5V
VCC C1+ C1 C1C2+ C2 C2-
VL V+ C3
T1OUT 5V/div
0 -5V 2V 0
MAX3380E MAX3381E
VC4
R1OUT 2V/div
T_ IN
T_ OUT
TIME (1s/div) VCC = VL = +2.5V, C1 = 0.1F, C2 = C3 = C4 = 1F, CLOAD = 1000pF
R_ OUT
R_ IN 5k
Figure 10. Loopback Test Results at 460kbps (VCC = +2.5V)
1000pF
FORCEON VCC FORCEOFF
GND
Figure 8. Loopback Test Circuit
12
______________________________________________________________________________________
+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
47F 0.1F
VCC
VL FORCEOFF
0.1F
C1+ C1-
FORCEON V+ 0.1F
0.1F VBATT CELL PHONE LOGIC LEVELS Tx RTS Rx CTS
C2+ C2-
V0.1F
MAX3380E/ MAX3381E
T1IN T2IN R1OUT R2OUT T1OUT T2OUT R1IN R2IN INVALID Tx
PERIPHERALS RS-232 LEVELS
CTS Rx RTS
I/O
Figure 11. Typical Application Circuit
Pin Configuration
TOP VIEW
C1+ 1 V+ 2 C1- 3 C2+ 4 C2- 5 V- 6 INVALID 7 T1IN 8 T2IN 9 R2OUT 10 20 VCC 19 FORCEOFF 18 GND 17 T1OUT
Chip Information
TRANSISTOR COUNT: 1467 PROCESS: BiCMOS
MAX3380E/ MAX3381E
16 T2OUT 15 R1IN 14 R2IN 13 VL 12 FORCEON 11 R1OUT
TSSOP
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13
+2.35V to +5.5V, 1A, 2Tx/2Rx RS-232 Transceivers with 15kV ESD-Protected I/O and Logic Pins MAX3380E/MAX3381E
Package Information
TSSOP.EPS
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 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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