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19-1529; Rev 1; 10/99
3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones
General Description
The MAX3386E 3V-powered EIA/TIA-232 and V.28/V.24 is a communications interface with low power requirements, high data-rate capabilities, and enhanced electrostatic discharge (ESD) protection. The MAX3386E has two receivers and three transmitters. All RS-232 inputs and outputs are protected to 15kV using the IEC 1000-4-2 Air-Gap Discharge method, 8kV using the IEC 1000-4-2 Contact Discharge method, and 15kV using the Human Body Model. A proprietary low-dropout transmitter output stage enables true RS-232 performance from a +3.0V to +5.5V supply with a dual charge pump. The charge pump requires only four small 0.1F capacitors for operation from a +3.3V supply. The MAX3386E is capable of running at data rates up to 250kbps while maintaining RS-232 compliant output levels. The MAX3386E has a unique VL pin that allows interoperation in mixed-logic voltage systems. Both input and output logic levels are pin programmable through the VL pin. The MAX3386E is available in a space-saving TSSOP package.
Features
o VL Pin for Compatibility with Mixed-Voltage Systems o 15kV ESD Protection on Rx Inputs and Tx Outputs o Low 300A Supply Current o Guaranteed 250kbps Data Rate o 1A Low-Power Shutdown o Meets EIA/TIA-232 Specifications Down to 3.0V
MAX3386E
Ordering Information
PART MAX3386ECUP MAX3386EEUP TEMP. RANGE 0C to +70C -40C to +85C PIN-PACKAGE 20 TSSOP 20 TSSOP
Applications
Subnotebook/Palmtop Computers PDAs and PDA Cradles Cell Phone Data Cables Battery-Powered Equipment Hand-Held Equipment Peripherals
+3.3V CBYPASS C1 0.1F
Typical Operating Circuit
20 1 C1+ 3 4 C1C2+ C2SHDN
19 VCC
12 VL V+ 2 C3 0.1F 6 C4 0.1F
MAX3386E
V-
Pin Configuration
TOP VIEW
C1+ 1 V+ 2 C1- 3 C2+ 4 C2- 5 V- 6 T1IN 7 T2IN 8 T3IN 9 R2OUT 10 20 SHDN 19 VCC 18 GND 17 T1OUT
C2 0.1F
5
7 T1IN TTL/CMOS INPUTS
T1OUT 17 T2OUT 16 T3OUT 15 VL RS-232 OUTPUTS
8 T2IN 9 T3IN
MAX3386E
11 R1OUT
R1IN 14 5k VL RS-232 INPUTS
16 T2OUT 15 T3OUT 14 R1IN 13 R2IN
5k TTL/CMOS OUTPUTS 10 R2OUT
R2IN 13
12 VL 11 R1OUT
GND 18
TSSOP ________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.
3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones MAX3386E
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V VL to GND...................................................-0.3V to (VCC + 0.3V) V+ to GND ................................................................-0.3V to +7V V- to GND .................................................................+0.3V to -7V V+ + V-(Note 1) .............................................................. +13V Input Voltages T_IN, SHDN to GND ...........................................-0.3V to +6V R_IN to GND ..................................................................25V Output Voltages T_OUT to GND............................................................13.2V R_OUT.....................................................-0.3V to (VL + 0.3V) Short-Circuit Duration T_OUT to GND........................Continuous Continuous Power Dissipation (TA = +70C) 20-Pin TSSOP (derate 7.0mW/C above +70C) .......559mW Operating Temperature Ranges MAX3386ECUP .................................................0C to +70C MAX3386EEUP ..............................................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+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.
DC ELECTRICAL CHARACTERISTICS
(VCC = VL = +3.0V to +5.5V; C1-C4 = 0.1F, tested at +3.3V 10%; C1 = 0.047F, C2-C4 = 0.33F, tested at +5.0V 10%; TA = TMIN to TMAX; unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25C.) PARAMETER Shutdown Supply Current Supply Current LOGIC INPUTS Input Logic Threshold Low T_IN, SHDN VL = 3.3V or 5.0V VL = 2.5V VL = 5.0V Input Logic Threshold High T_IN, SHDN VL = 3.3V VL = 2.5V VL = 1.8V Transmitter Input Hysteresis Input Leakage Current RECEIVER OUTPUTS Output Leakage Currents Output Voltage Low Output Voltage High RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance 2 TA = +25C 3 TA = +25C IOUT = -1mA TA = +25C VL = 5.0V VL = 2.5V or 3.3V VL = 5.0V VL = 2.5V or 3.3V -25 0.8 0.6 1.2 1.5 1.8 1.5 0.5 5 7 2.4 2.4 +25 V V V V k R_OUT, receivers disabled IOUT = 1.6mA IOUT = -1mA VL 0.6 VL 0.1 0.05 10 0.4 A V V T_IN, SHDN 2.4 2.0 1.4 0.9 0.5 0.01 1 V A V 0.8 0.6 V SYMBOL CONDITIONS SHDN = GND, all inputs at VCC or GND SHDN = VCC, no load MIN TYP 1 0.3 MAX 10 1 UNITS A mA
DC CHARACTERISTICS (VCC = +3.3V or +5V, TA = +25C)
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = VL = +3.0V to +5.5V; C1-C4 = 0.1F, tested at +3.3V 10%; C1 = 0.047F, C2-C4 = 0.33F, tested at +5.0V 10%; TA = TMIN to TMAX; unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25C.) PARAMETER TRANSMITTER OUTPUTS RECEIVER INPUTS Output Voltage Swing Output Resistance Output Short-Circuit Current Output Leakage Current ESD PROTECTION Human Body Model R_IN, T_OUT ESD Protection IEC 1000-4-2 Air-Gap Discharge method IEC 1000-4-2 Contact Discharge method 15 15 8 kV All transmitter outputs loaded with 3k to ground VCC = V+ = V- = 0, transmitter output = 2V VT_OUT = 0 VT_OUT = 12V, transmitters disabled; VCC = 0 or 3.0V to 5.5V 5 300 5.4 10M 60 25 V mA A SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX3386E
TIMING CHARACTERISTICS
(VCC = VL = +3V to +5.5V; C1-C4 = 0.1F, tested at +3.3V 10%; C1 = 0.047F, C2-C4 = 0.33F, tested at +5.0V 10%; TA = TMIN to TMAX; unless otherwise noted. Typical values are at VCC = VL = +3.3V, TA = +25C.) PARAMETER Maximum Data Rate Receiver Propagation Delay Receiver Output Enable Time Receiver Output Disable Time Time to Exit Shutdown Transmitter Skew Receiver Skew Transition-Region Slew Rate VT_OUT > 3.7V tPHL - tPLH (Note 2) tPHL - tPLH VCC = 3.3V, TA = +25C, RL = 3k to 7k, measured from +3V to -3V or -3V to +3V CL = 150pF to 1000pF CL = 150pF to 2500pF 6 4 tPHL tPLH SYMBOL CONDITIONS RL = 3k, CL = 1000pF, one transmitter switching Receiver input to receiver output, CL = 150pF MIN 250 0.15 0.15 200 200 100 100 50 30 V/s 30 TYP MAX UNITS kbps s ns ns s ns ns
Note 2: Transmitter skew is measured at the transmitter zero crosspoint.
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones MAX3386E
Typical Operating Characteristics
(VCC = VL = +3.3V, TA = +25C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX3386E toc 01
SLEW RATE vs. LOAD CAPACITANCE
14 12 SLEW RATE (V/s) SLEW RATE 10 8 6 4 SLEW RATE +
MAX3386E toc 02
7.5 5.0 OUTPUT VOLTAGE (V) 2.5 0 -2.5 -5.0 -7.5 0 1000 2000 3000 4000 DATA RATE = 250kbps LOAD = 3k IN PARALLEL WITH CL
16
2 0 5000 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF) LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE vs. DATA RATE
MAX3386E toc 03
SUPPLY CURRENT vs. LOAD CAPACITANCE
LOAD = 3k, ONE TRANSMITTER SWITCHING AT DATA RATE, OTHER 250kbps TRANSMITTERS AT 1/8 DATA RATE 120kbps
MAX3386E toc 04
7.5 5.0 OUTPUT VOLTAGE (V) 2.5 0 -2.5 -5.0 -7.5 0 50 100 150 200 LOAD = 3k, 1000pF ONE TRANSMITTER SWITCHING AT DATA RATE, OTHER TRANSMITTERS AT 1/8 DATA RATE
60 50 SUPPLY CURRENT (mA) 40 30 20 10 0
20kbps
250
0
1000
2000
3000
4000
5000
DATA RATE (kbps)
LOAD CAPACITANCE (pF)
4
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones
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+ C2VT1IN T2IN T3IN R2OUT R1OUT VL R2IN RS-232 Receiver Inputs R1IN T3OUT T2OUT T1OUT GND VCC SHDN Ground +3.0V to +5.5V Supply Voltage Shutdown Input. 0 = shutdown, 1 = normal operation. RS-232 Transmitter Outputs TTL/CMOS Receiver Outputs. Swing between 0 and VL. Logic-Level Supply. All CMOS inputs and outputs are referenced to this supply. TTL/CMOS Transmitter Inputs FUNCTION Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor +5.5V Supply Generated by the Charge Pump Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor Positive Terminal of the Inverting Charge-Pump Capacitor Negative Terminal of the Inverting Charge-Pump Capacitor -5.5V Generated by the Charge Pump
MAX3386E
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones MAX3386E
Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3386E's internal power supply consists of a regulated dual charge pump that provides output voltages of +5.5V (doubling charge pump) and -5.5V (inverting charge pump), regardless of the input voltage (VCC) over a +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. These RS-232 output stages are turned off (high impedance) when the device is in shutdown mode. When the power is off, the MAX3386E permits the outputs to be driven up to 12V. The transmitter inputs do not have pull-up resistors. Connect unused inputs to GND or VL.
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic output levels. The MAX3386E's receivers have inverting three-state outputs, which depend on the shutdown state of the device.
Shutdown Mode
Supply current falls to less than 1A when the MAX3386E is placed in shutdown mode (SHDN logic low). When shut down, the device's charge pumps are turned off, V+ decays to VCC, V- is pulled to ground, and the transmitter outputs are disabled (high impedance). The time required to exit shutdown is typically 100s, as shown in Figure 2. Connect SHDN to VCC if the shutdown mode is not used. In shutdown mode, the receiver outputs are high impedance (Table 1).
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The MAX3386E's transmitters guarantee a 250kbps data rate with worst-case loads of 3k in parallel with 1000pF, providing compatibility with PC-to-PC communication software (such as LapLinkTM). Transmitters can be paralleled to drive multiple receivers or mice. Figure 1 shows a complete system connection.
Table 1. Shutdown Logic Truth Table
SHDN TRANSMITTER OUTPUTS High-Z Active RECEIVER OUTPUTS High-Z Active CHARGE PUMP Inactive Active
POWERMANAGEMENT UNIT OR KEYBOARD CONTROLLER I/O CHIP POWER SUPPLY
SHDN
L H
VL
VCC
MAX3386E
5V/div T2
I/O CHIP WITH UART CPU
RS-232
2V/div
VCC = 3.3V C1-C4 = 0.1F 50s/div
T1
Figure 1. Interface Under Control of PMU LapLink is a trademark of Traveling Software.
6
Figure 2. Transmitter Outputs when Exiting Shutdown
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones
VL Logic Supply Input
Unlike other RS-232 interface devices where the receiver outputs swing between 0 and VCC, the MAX3386E features a separate logic supply input (VL) that sets VOH for the receiver outputs and sets thresholds for the receiver inputs. This feature allows a great deal of flexibility in interfacing to many different types of systems with different logic levels. Connect this input to the host logic supply (1.8V VL VCC). Also see the Typical PDA/Cell-Phone Application section.
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE RD 1500 DISCHARGE RESISTANCE DEVICE UNDER TEST
MAX3386E
Cs 100pF
STORAGE CAPACITOR
15kV ESD Protection
As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges (ESDs) encountered during handling and assembly. The MAX3386E's driver outputs and receiver inputs have extra protection against static electricity. 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 powered down. After an ESD event, Maxim's "E" version devices keep working without latchup, 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 outputs and receiver inputs of this product family are characterized for protection to the following limits: 1) 15kV using the Human Body Model 2) 8kV using the Contact Discharge method specified in IEC 1000-4-2 3) 15kV using IEC 1000-4-2's Air-Gap Discharge method
Figure 3a. Human Body ESD Test Model
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
tDL 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.
Figure 3b. Human Body Current Waveform
Human Body Model
Figure 3a shows the Human Body Model, and Figure 3b 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 MAX3386E helps you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without the need for 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 model. Hence, the ESD withstand voltage measured to IEC 1000-4-2 is generally lower than that measured using the Human Body Model. Figure 4a shows the IEC 1000-4-2 model, and Figure 4b 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.
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones MAX3386E
Machine Model
RC 50M to 100M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
Cs 150pF
STORAGE CAPACITOR
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
Figure 4a. IEC 1000-4-2 ESD Test Model
I 100% 90%
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, and C4 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 larger nominal value. The capacitor's equivalent series resistance (ESR), which usually rises at low temperatures, influences the amount of ripple on V+ and V-.
I PEAK
10% t R = 0.7ns to 1ns t 30ns 60ns
Power-Supply Decoupling
In most circumstances, a 0.1F bypass capacitor is adequate. In applications that are sensitive to powersupply 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.
Figure 4b. IEC 1000-4-2 ESD Generator Current Waveform
Operation Down to 2.7V
Transmitter outputs will meet EIA/TIA-562 levels of 3.7V with supply voltages as low as +2.7V.
Table 2. Minimum Required Capacitor Values
VCC (V) 3.0 to 3.6 4.5 to 5.5 3.0 to 5.5 C1 (F) 0.1 0.047 0.22 C2, C3, C4 (F) 0.1 0.33 1
Transmitter Outputs when Exiting Shutdown
Figure 2 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 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 V- exceeds approximately 3V.
8
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones
High Data Rates
The MAX3386E maintains the RS-232 5.0V minimum transmitter output voltage even at high data rates. Figure 5 shows a transmitter loopback test circuit. Figure 6 shows a loopback test result at 120kbps, and Figure 7 shows the same test at 250kbps. For Figure 6, all transmitters were driven simultaneously at 120kbps into RS-232 loads in parallel with 1000pF. For Figure 7, a single transmitter was driven at 250kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 1000pF.
VCC 0.1F
MAX3386E
VCC C1+ C1 C1C2+ C2 C2V+
MAX3386E
V-
C3
Interconnection with 3V and 5V Logic
The MAX3386E can directly interface with various 5V logic families, including ACT and HCT CMOS. The logic voltage power-supply pin VL sets the output voltage level of the receivers and the input thresholds of the transmitters.
C4
T_ IN
T_ OUT
Typical PDA/Cell-Phone Application
The MAX3386E is designed with PDA applications in mind. Two transmitters and two receivers handle standard full-duplex communication protocol, while an extra transmitter allows a ring indicator (RI) signal to alert the UART on the PC. Without the ring indicator transmitter, solutions for these applications would require softwareintensive polling of the cradle inputs. The RI signal is generated when a PDA, cellular phone, or other "cradled" device is plugged into its cradle. This generates a logic-low signal to RI transmitter input, creating +6V at the ring indicate pin. The PC's UART RI input is the only pin that can generate an interrupt from signals arriving through the RS-232 port. The interrupt routine for this UART will then service the RS-232 full-duplex communication between the PDA and the PC. As cell phone design becomes more like that of PDAs, cell phones will require similar docking ability and communication protocol. Cell phones operate on a single lithium-ion (Li+) battery and work with a power-supply voltage of +2.7V to +4V. The baseband logic coming from the phone connector can be as low as 1.8V at the transceivers. To prevent forward biasing of a device internal to the cell phone, the MAX3386E comes with a logic power-supply pin (VL) that limits the logic levels presented to the phone. The receiver outputs will sink to zero for low outputs, but will not exceed VL for logic highs. The input logic levels for the transmitters are also altered, scaled by the magnitude of the VL input. The device will work with V L as low as 1.8V before the charge-pump noise will begin to cause the transmitter outputs to oscillate. This is useful with cell phones and other power-efficient devices with core logic voltage levels that go as low as 1.8V.
R_ OUT
R_ IN 5k 1000pF
VCC
SHDN
GND
Figure 5. Loopback Test Circuit
T1IN
5V/div
5V/div T1OUT
R1OUT VCC = 3.3V 2s/div
5V/div
Figure 6. Loopback Test Results at 120kbps
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones MAX3386E
T1IN
5V/div
T1OUT
5V/div
R1OUT VCC = 3.3V 2s/div
5V/div
Figure 7. Loopback Test Results at 250kbps
Chip Information
TRANSISTOR COUNT: 1267
10
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones
Package Information
TSSOP.EPS
MAX3386E
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3.0V, 15kV ESD-Protected RS-232 Transceiver for PDAs and Cell Phones MAX3386E
NOTES
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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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