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19-1845; Rev 1; 9/01
2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones
General Description
The MAX3388E/MAX3389E are 2.5V-powered EIA/TIA232 and V.28/V.24 communications interfaces with low power requirements, high data-rate capabilities, and enhanced electrostatic discharge (ESD) protection. The MAX3388E/MAX3389E have 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. In addition to the traditional RS-232 I/O, these devices have dedicated logic-level I/O pins for additional device-todevice handshaking. During shutdown the logic-level I/O pins are active for the MAX3389E. An internal 62 switch is provided to switch power to external circuitry or modules. A proprietary low-dropout transmitter output stage enables RS-232 compatible performance from a +2.35V to +3.0V supply with a dual charge pump. The charge pump requires only four small 0.1F capacitors for operation from a +2.5V supply. The MAX3388E/MAX3389E are capable of running at data rates up to 460kbps while maintaining RS-232-compatible output levels. The MAX3388E/MAX3389E have 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 MAX3388E/MAX3389E are available in a space-saving TSSOP package.
Features
o VL Pin for Compatibility with Mixed-Voltage Systems o Additional I/O for Hot-Sync Applications o 15kV ESD Protection on Rx Inputs, Tx Outputs, LIN, and SWIN o Low 300A Supply Current o Guaranteed 460kbps Data Rate o 1A Low-Power Shutdown o Integrated Switch for Powering Remote Circuitry o Flow-Through Pinout o LOUT Active During Shutdown (MAX3389E)
MAX3388E/MAX3389E
Applications
Subnotebook/Palmtop Computers PDAs and PDA Cradles Cell Phone Data Cables Battery-Powered Equipment Hand-Held Equipment Peripherals
Ordering Information
PART TEMP. RANGE 0C to +70C -40C to +85C 0C to +70C -40C to +85C PIN-PACKAGE 24 TSSOP 24 TSSOP 24 TSSOP 24 TSSOP MAX3388ECUG MAX3388EEUG MAX3389ECUG
Typical Operating Circuit
+2.5V CBYPASS C1 0.1F 1 C1+ 3 4 C2 0.1F 5 C1C2+ C2T1OUT 21 8 T2IN 9 T3IN VL 13 R1OUT R1IN 18 5k VL 12 R2OUT 10 LOUT R2IN 17 5k LIN 16 SHDN 11 = 15kV ESD PROTECTION SWOUT 30k SWIN 15 T2OUT 20 T3OUT 19 RS-232 I/O 24 SHDN 23 VCC 14 VL V+ 2 C3 0.1F
MAX3389EEUG
MAX3388E MAX3389E
V-
6 C4 0.1F
Pin Configuration
TOP VIEW
C1+ 1 V+ 2 C1- 3 C2+ 4 C2- 5 V- 6 T1IN 7 T2IN 8 T3IN 9 LOUT 10 SWOUT 11 R2OUT 12 24 SHDN 23 VCC 22 GND 21 T1OUT
7 T1IN
MAX3388E MAX3389E
20 T2OUT 19 T3OUT 18 R1IN 17 R2IN 16 LIN 15 SWIN 14 VL 13 R1OUT
GND 22
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.
TSSOP
________________________________________________________________ Maxim Integrated Products
1
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.
2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones MAX3388E/MAX3389E
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, LIN to GND.......................................-0.3V to +6V R_IN to GND .....................................................................25V SWIN to GND...........................................-0.3V to (VCC + 0.3V) Output Voltages T_OUT to GND...............................................................13.2V R_OUT, SWOUT, LOUT to GND ................-0.3V to (VL + 0.3V) Short-Circuit Duration T_OUT to GND........................Continuous Continuous Power Dissipation (TA = +70C) 24-Pin TSSOP (derate 12.2mW/C above +70C) ........975mW Operating Temperature Ranges MAX338_ECUG ...................................................0C to +70C MAX338_EEUG.................................................-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.
DC ELECTRICAL CHARACTERISTICS
(VCC = VL = +2.35V to +3.0V, C1-C4 = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +2.5V, TA = +25C.) PARAMETER Shutdown Supply Current Supply Current LOGIC INPUTS (T_IN, SHDN) Input Logic Low Input Logic High Transmitter Input Hysteresis Input Leakage Current RECEIVER OUTPUTS Output Leakage Current Output Voltage Low Output Voltage High RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance TRANSMITTER OUTPUTS Output Voltage Swing Output Resistance Output Short-Circuit Current All transmitter outputs loaded with 3k to ground VCC = 0, transmitter output = 2V VT_OUT = 0 3.7 300 4.2 10M 60 V mA TA = +25C 3 TA = +25C, VL = +2.5V TA = +25C, VL = +2.5V -25 0.6 1.1 1.8 0.7 5 7 2.4 +25 V V V V k R_OUT, SHDN = 0 IOUT = 1.6mA IOUT = -1mA VL 0.6 VL 0.13 0.05 10 0.4 A V V VL = +2.5V VL = +2.5V 1.5 0.4 0.01 1 0.6 V V V A SYMBOL CONDITIONS SHDN = GND, all inputs at GND SHDN = VCC, no load MIN TYP 1 0.3 MAX 10 1 UNITS A mA DC CHARACTERISTICS (VCC = +2.5V, TA = +25C)
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2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = VL = +2.35V to +3.0V, C1-C4 = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +2.5V, TA = +25C.)
PARAMETER Output Leakage Current HANDSHAKING I/O (LIN, LOUT) Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance Output Voltage Low Output Leakage Current SWITCH (SWIN, SWOUT) Input Voltage Range On-Resistance Off-Leakage Current Turn-On Time Turn-Off Time ESD PROTECTION Human Body Model R_IN, T_OUT, LIN, SWIN ESD Protection IEC 1000-4-2 Air-Gap Discharge method IEC 1000-4-2 Contact Discharge method 15 15 8 kV SHDN = 0 0.18 0.7 0 62 VCC 100 1 V A s s TA = +25oC LOUT, ISINK = 1.6mA LOUT = VL, LIN = low or float 20 LIN, VL = +2.5V, TA = +25C LIN, VL = +2.5V, TA = +25C 0 0.6 1.1 1.7 0.6 40 0.4 10 2 VCC V V V V k V A SYMBOL CONDITIONS VT_OUT = 12V, transmitters disabled, VCC = 0 or +2.5V MIN TYP MAX 25 UNITS A
MAX3388E/MAX3389E
TIMING CHARACTERISTICS
(VCC = VL = +2.35V to +3.0V, C1-C4 = 0.1F, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL = +2.5V, TA = +25C.) PARAMETER SYMBOL CONDITIONS RL = 3k, CL = 1000pF, one transmitter switching Maximum Data Rate tPHL - tPLH 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 RL = 3k, CL = 1000pF (Note 3) tPHL - tPLH VCC = +2.5V, TA = +25C, CL = 150pF to RL = 3k to 7k, 1000pF measured from +3V CL = 150pF to to -3V or -3V to +3V, 2500pF one transmitter switching tPHL tPLH RL = 3k, CL = 150pF, one transmitter switching (Note 2) Receiver input to receiver output, CL = 150pF 460 0.15 0.15 200 200 30 100 50 6 4 30 V/s 30 s ns ns s ns ns MIN 250 kbps TYP MAX UNITS
Note 2: Guaranteed by correlation. Note 3: Transmitter skew is measured at the transmitter zero crosspoint. _______________________________________________________________________________________ 3
2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones MAX3388E/MAX3389E
Typical Operating Characteristics
(VCC = VL = +2.5V, TA = +25C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX3388E toc01
SLEW RATE vs. LOAD CAPACITANCE
14 12 SLEW RATE (V/s) SLEW RATE 10 8 6 4 2 SLEW RATE +
MAX3386E toc02
5.0
16
OUTPUT VOLTAGE (V)
2.5 DATA RATE = 460kbps LOAD = 3k IN PARALLEL 0
-2.5
-5.0 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF)
0 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE vs. DATA RATE
MAX3388E toc03
SUPPLY CURRENT vs. LOAD CAPACITANCE
LOAD = 3k ONE TRANSMITTER SWITCHING AT DATA RATE, OTHER TRANSMITTERS AT 1/8 DATA RATE
MAX3388E toc04
5.0
60 50 SUPPLY CURRENT (mA) 40 30 20 10
OUTPUT VOLTAGE (V)
2.5 LOAD = 3k, 1000pF ONE TRANSMITTER SWITCHING AT DATA RATE, OTHER TRANSMITTERS AT 1/8 DATA RATE
460kbps
0
240kbps
-2.5 20kbps
-5.0 0 50 100 150 200 250 300 350 400 450 DATA RATE (kbps)
0 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF)
LIN TO LOUT tPD
MAX3388E toc05
ON-RESISTANCE vs. SWIN VOLTAGE
TA = +85C 65 TA = +25C RON () 60
MAX3388E toc06
70
LIN
1V/div
55 TA = -40C 50 LOUT RPULLUP = 1k 45 200ns/div 0 0.5 1.0 1.5 2.0 2.5 VSWIN (V)
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2.5V, 15kV ESD-Protected RS-232 Transceivers 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 NAME C1+ V+ C1C2+ C2VT1IN, T2IN, T3IN LOUT SWOUT R2OUT, R1OUT VL SWIN LIN R2IN, R1IN T3OUT, T2OUT, T1OUT GND VCC SHDN FUNCTION Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor +4.2V 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 -4.2V Supply Generated by the Charge Pump CMOS Transmitter Inputs Handshaking Output. This output is active during shutdown for the MAX3389E. Switch Output CMOS Receiver Outputs. Swing between 0 and VL. Logic-Level Supply. All CMOS inputs and outputs are referred to this supply. VL = +1.8V to +3.0V. Switch Input. Handshaking Input. This input is active during shutdown for the MAX3389E. RS-232 Receiver Inputs
MAX3388E/MAX3389E
19, 20, 21 22 23 24
RS-232 Transmitter Outputs Ground +2.35V to +3V Supply Voltage Shutdown Input. 0 = shutdown, switch open; 1 = normal operation, switch closed.
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2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones MAX3388E/MAX3389E
Table 1. Shutdown Logic Truth Table
SHDN L H TRANSMITTER OUTPUTS High-Z Active RECEIVER OUTPUTS High-Z Active CHARGE PUMP Inactive Active SWITCH Open Closed LOUT MAX3388E High-Z LIN MAX3389E LIN LIN
POWERMANAGEMENT UNIT OR KEYBOARD CONTROLLER I/O CHIP POWER SUPPLY
SHDN
5V/div T1
VL
MAX3388E MAX3389E
2V/div
T2 VCC = +2.5V C1-C4 = 0.1F CL = 1000pF, RL = 3k
RS-232
I/O CHIP WITH UART CPU
10s/div
Figure 2. Transmitter Outputs when Exiting Shutdown
Figure 1. Interface Under Control of PMU
Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3388E/MAX3389E's internal power supply consists of a regulated dual charge pump that provides output voltages of +4.2V (doubling charge pump) and 4.2V (inverting charge pump), regardless of the input voltage (VCC) over a +2.5V to +3.0V range. The charge pumps operate in a discontinuous mode: if the output voltages are less than 4.2V, the charge pumps are enabled; if the output voltages exceed 4.2V, the charge pumps are disabled. Each charge pump requires flying capacitors (C1, C2) and reservoir capacitors (C3, C4) to generate the V+ and V- supplies.
The MAX3388E/MAX3389E's transmitters guarantee a 250kbps data rate with loads of 3k in parallel with 1000pF and 460kbps data rate with loads of 3k in parallel with 150pF. Figure 1 shows a complete system connection. These RS-232 output stages are turned off (high impedance) when the devices are in shutdown mode. When the power is off, the MAX3388E/MAX3389E permit the outputs to be driven up to 12V. The transmitter inputs do not have pullup resistors. Connect unused inputs to GND or VL.
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic output levels. The MAX3388E/MAX3389E's receivers have inverting outputs. The outputs are high impedance in shutdown.
Shutdown Mode
Supply current falls to less than 1A when the MAX3388E/MAX3389E are 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, the switch is opened, and the transmitter outputs are disabled (high impedance). The time required to exit
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to 3.7V EIA/TIA-232-compatible levels.
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2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones
shutdown is typically 30s, 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).
MAX3388E/MAX3389E
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1500 DISCHARGE RESISTANCE DEVICE UNDER TEST
VL Logic Supply Input
Unlike other RS-232 interface devices where the receiver outputs swing between 0 and V CC, the MAX3388E/ MAX3389E feature a separate logic supply input (VL) that sets VOH for the receiver outputs and sets thresholds for the transmitter 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.
Cs 100pF
STORAGE CAPACITOR
Figure 3a. Human Body ESD Test Model
15kV ESD Protection
As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against ESDs encountered during handling and assembly. The MAX3388E/ MAX3389E's driver outputs, receiver inputs, the handshaking input LIN, and the switch terminal SWIN 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
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
tDL CURRENT WAVEFORM
Figure 3b. Human Body Current Waveform
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 MAX3388E/MAX3389E helps 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 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.
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 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.
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2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones MAX3388E/MAX3389E
RC 50M to 100M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
The Air-Gap test involves approaching the device with a charged probe. The contact discharge method connects the probe to the device before the probe is energized.
Machine Model
The Machine Model for ESD tests all pins using a 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.
Cs 150pF
STORAGE CAPACITOR
__________Applications Information
Figure 4a. IEC 1000-4-2 ESD Test Model
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 2.5V operation (Table 2). 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 100% 90%
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
Table 2. Minimum Required Capacitor Values
VCC (V) 2.5 to 3.0 C1-C4 (F) 0.1
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 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 2.5V.
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2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones
High Data Rates
The MAX3388E/MAX3389E maintain RS-232-compatible transmitter output voltages even at high data rates. Figure 5 shows a transmitter loopback test circuit. Figure 6 shows a loopback test result at 250kbps, and Figure 7 shows the same test at 460kbps. For Figure 6, all transmitters were driven simultaneously at 250kbps into RS-232 loads in parallel with 1000pF. For Figure 7, a single transmitter was driven at 460kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 150pF.
VCC 0.1F
MAX3388E/MAX3389E
VCC C1+ C1 C1C2+ C2 C2V+ C3
Power Switch
The MAX3388E/MAX3389E contain an internal switch for powering external circuitry. This can be used to power hot-sync circuitry or other low-power circuitry. The switch on- resistance is typically 62. The SWIN side of the switch is ESD protected to 15kV.
MAX3388E MAX3389E
V-
C4
T_ IN
T_ OUT
Logic-Level I/O
In addition to the traditional RS-232 I/O, the MAX3388E/MAX3389E have a logic-level transceiver from the RS-232 connector side to the CMOS-logic side. The input impedance is typically 30k, and the output is open drain. The logic level I/O is active during shutdown for the MAX3389E. This I/O transceiver is useful for hot syncing or other dedicated communication capability. The input is ESD protected to 15kV.
R_ OUT R_ IN 5k VCC
CL
SHDN
GND
Typical PDA/Cell-Phone Application
The MAX3388E/MAX3389E 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 software-intensive 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 +3.7V 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 generate a regulated output voltage of +2.35V to +3V from the phone connector. 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 MAX3388E/MAX3389E come with a logic powersupply pin (VL) that limits the logic levels presented to
Figure 5. Loopback Test Circuit
T1IN
2V/div
T1OUT
5V/div
R1OUT CL = 1000pF 1s/div
5V/div
Figure 6. Loopback Test Results at 250kbps
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9
2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones MAX3388E/MAX3389E
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 devices will work with VL as low as 1.8V. This is useful with cell phones and other power-efficient devices with core logic voltage levels that go as low as 1.8V.
T1IN
2V/div
T1OUT
5V/div
Chip Information
TRANSISTOR COUNT: 1323
R1OUT CL = 150pF 1s/div 5V/div
Figure 7. Loopback Test Results at 460kbps
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2.5V, 15kV ESD-Protected RS-232 Transceivers for PDAs and Cell Phones
Package Information
TSSOP.EPS
MAX3388E/MAX3389E
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________11 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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