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19-1473; Rev 0; 4/99
15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors
________________General Description
The MAX3233E/MAX3235E are EIA/TIA-232 and V.28/V.24 communications interfaces with automatic shutdown/ wake-up features, high data-rate capabilities, and enhanced electrostatic discharge (ESD) protection. All transmitter outputs and receiver inputs are protected to 15kV using IEC 1000-4-2 Air-Gap Discharge, to 8kV using IEC 1000-4-2 Contact Discharge, and to 15kV using the Human Body Model. The MAX3233E operates from a +3.3V supply; the MAX3235E operates from +5.0V. All devices achieve a 1A supply current using Maxim's revolutionary AutoShutdown PlusTM feature. These devices automatically enter a low-power shutdown mode when the following two conditions occur: either the RS-232 cable is disconnected or the transmitters of the connected peripherals are inactive, and the UART driving the transmitter inputs is inactive for more than 30 seconds. They turn on again when they sense a valid transition at any transmitter or receiver input. AutoShutdown Plus saves power without changes to the existing BIOS or operating system. The MAX3233E/MAX3235E have internal dual charge pumps requiring no external capacitors. Both transceivers have a proprietary low-dropout transmitter output stage that enables true RS-232 performance from a +3.0V to +3.6V supply for the MAX3233E or a +4.5V to +5.5V supply for the MAX3235E. These devices are guaranteed to operate up to 250kbps. Both are available in space-saving 20-pin wide SO or plastic DIP packages.
____________________________Features
o ESD Protection for RS-232 I/O Pins 15kV--Human Body Model 8kV--IEC 1000-4-2, Contact Discharge 15kV--IEC 1000-4-2, Air-Gap Discharge o Latchup Free o 1A Supply Current o AutoShutdown Plus--1997 EDN Magazine Innovation of the Year o Single-Supply Operation +3.0V to +3.6V (MAX3233E) +4.5V to +5.5V (MAX3235E) o 250kbps Guaranteed Data Rate o 6V/s Guaranteed Slew Rate o Meets EIA/TIA-232 Specifications Down to 3.0V (MAX3233E) o Internal Charge-Pump Capacitors
MAX3233E /MAX3235E
Pin Configuration/ Functional Diagram
R2OUT
1 2 3 4 5 6 7 8 9 10
20
MAX3233E MAX3235E
R2IN
INVALID T2IN T1IN FORCEON R1OUT T1OUT
19 18 17 16 15 14 13 12 11
T2OUT GND VC2C2+ C1C1+ V+ V+
________________________Applications
Subnotebook and Palmtop Computers Cellular Phones Battery-Powered Equipment Hand-Held Equipment Peripherals Embedded Systems
CHARGE PUMP
_______________Ordering Information
R1IN
PART MAX3233ECWP MAX3233ECPP MAX3233EEWP MAX3233EEPP
TEMP. RANGE 0C to +70C 0C to +70C -40C to +85C -40C to +85C
PIN-PACKAGE 20 SO 20 Plastic DIP 20 SO 20 Plastic DIP
VCC FORCEOFF
Ordering Information continued at end of data sheet. AutoShutdown Plus is a trademark of Maxim Integrated Products.
Covered by U.S. Patent numbers 4,636,930; 4,679,134; 4,777,577;
SO/DIP
4,797,899; 4,809,152; 4,897,774; 4,999,761; 5,649,210; and other patents pending.
Typical Operating Circuit appears at end of data sheet.
1
________________________________________________________________ Maxim Integrated Products
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.
15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
ABSOLUTE MAXIMUM RATINGS
VCC to GND (MAX3233E).........................................-0.3V to +4V VCC to GND (MAX3235E).........................................-0.3V to +6V V+ to GND (Note 1) ..................................................-0.3V to +7V V- to GND (Note 1) ...................................................+0.3V to -7V V+ + |V-| (Note 1).................................................................+13V Input Voltages T_IN, FORCEON, FORCEOFF to GND....................-0.3V to +6V R_IN to GND ...................................................................25V Output Voltages T_OUT to GND.............................................................13.2V R_OUT, INVALID to GND ......................-0.3V to (VCC + 0.3V) Short-Circuit Duration T_OUT to GND ......................................................Continuous Continuous Power Dissipation (TA = +70C) Wide SO (derate 10mW/C above +70C)..................800mW Plastic DIP (derate 11.11mW/C above +70C) .........889mW Operating Temperature Ranges MAX323_EC_P ...................................................0C to +70C MAX323_EE_P ................................................-40C to +85C 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.
ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +3.6V for MAX3233E, VCC = +4.5V to +5.5V for MAX3235E; TA = TMIN to TMAX; unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Supply Current, AutoShutdown Plus Supply Current, Shutdown Supply Current, AutoShutdown Plus Disabled LOGIC INPUTS AND RECEIVER OUTPUTS Input Logic Threshold Low Input Logic Threshold High Transmitter Input Hysteresis Input Leakage Current Output Voltage Low Output Voltage High RECEIVER INPUTS Input Voltage Range Input Threshold Low Input Threshold High Input Hysteresis Input Resistance TA = +25C 3 TA = +25C TA = +25C VCC = 3.3V, MAX3233E VCC = 5.0V, MAX3235E VCC = 3.3V, MAX3233E VCC = 5.0V, MAX3235E -25 0.6 0.8 1.0 1.3 1.5 1.8 0.5 5 7 2.4 2.4 +25 V V V V k T_IN, FORCEON, FORCEOFF IOUT = 1.6mA IOUT = -1.0mA VCC - 0.6 VCC - 0.1 T_IN, FORCEON, FORCEOFF T_IN, FORCEON, FORCEOFF VCC = 3.3V, MAX3233E VCC = 5.0V, MAX3235E 2 2.4 0.5 0.01 1 0.4 0.8 V V V A V V SYMBOL CONDITIONS FORCEON = GND, FORCEOFF = VCC, all R_IN idle, all T_IN idle FORCEOFF = GND FORCEON = FORCEOFF = VCC, no load MIN TYP MAX UNITS DC CHARACTERISTICS (VCC = 3.3V for MAX3233E, VCC = 5.0V for MAX3235E, TA = +25C.) 1 1 0.3 10 10 1 A A mA
2
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3.0V to +3.6V for MAX3233E, VCC = +4.5V to +5.5V for MAX3235E; TA = TMIN to TMAX; unless otherwise noted. Typical values are at TA = +25C.) PARAMETER TRANSMITTER OUTPUTS Output Voltage Swing Output Resistance Output Short-Circuit Current VOUT = 12V transmitters disabled VCC = 0 or +3.0V to 3.6V (MAX3233E) VCC = 0 or +4.5V to 5.5V (MAX3235E) 15 8 15 Positive threshold Negative threshold -2.7 -0.3 0.3 0.4 VCC - 0.6 1 MAX3233E MAX3235E 70 50 100 15 30 60 2.7 kV All transmitter outputs loaded with 3k to ground VCC = V+ = V- = 0, transmitter outputs = 2V 5 300 5.4 10M 60 25 A 25 V mA SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX3233E/MAX3235E
Output Leakage Current
ESD PROTECTION IEC1000-4-2 Air Discharge R_IN, T_OUT IEC1000-4-2 Contact Discharge Human Body Model AutoShutdown PLUS (FORCEON = GND, FORCEOFF = VCC) Receiver Input Threshold to INVALID Output High Receiver Input Threshold to INVALID Output Low INVALID Output Voltage Low INVALID, Output Voltage High Receiver Positive or Negative Threshold to INVALID High Receiver Positive or Negative Threshold to INVALID Low Receiver or Transmitter Edge to Transmitters Enabled tINVH tINVL tWU Figure 3a Figure 3a IOUT = -1.6mA IOUT = -1.0mA Figure 3b Figure 3b Figure 3b (Note 2) V V V V s s s sec
Receiver or Transmitter Edge to tAUTOSHDN Figure 3b (Note 2) Transmitters Shut Down
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
TIMING CHARACTERISTICS (continued)
(VCC = +3.0V to +3.6V for MAX3233E, VCC = +4.5V to +5.5V for MAX3235E; TA = TMIN to TMAX; unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Maximum Data Rate tPHL Receiver Propagation Delay tPLH Receiver Output Enable Time Receiver Output Disable Time Transmitter Skew Receiver Skew tPHL - tPLH tPHL - tPLH SYMBOL CONDITIONS RL = 3k, CL = 1000pF, one transmitter switching MAX3233E R_IN to R_OUT, CL = 150pF Normal operation Normal operation (Note 3) MAX3233E MAX3235E MAX3235E MAX3233E MAX3235E MIN 250 70 100 250 150 200 200 150 180 50 ns ns ns ns ns ns TYP MAX UNITS kbps
VCC = 3.3V (MAX3233E), CL = 150pF 6 30 VCC = 5.0V (MAX3235E), to 1000pF TA = +25C, Transition-Region Slew Rate Note 2: A transmitter/receiver edge is defined asRLtransition 7k, a = 3k to through the transmitter/receiver input logic thresholds. Note 3: Transmitter skew is measured at the transmitter zero cross points. measured from +3V to -3V CL = 150pF 4 30 to 2500pF or -3V to +3V
V/s
__________________________________________Typical Operating Characteristics
(VCC = +3.3V for MAX3233E, VCC = +5.0V for MAX3235E; 250kbps data rate; all transmitters loaded with 3k and CL; TA = +25C; unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE
MAX3233E/35Etoc01
OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE
MAX3233E/35E toc02
SLEW RATE vs. LOAD CAPACITANCE
14 12 SLEW RATE (V/s) SLEW RATE 10 8 6 4 SLEW RATE +
MAX3233E/35Etoc01
10.0 TRANSMITTER OUTPUT VOLTAGE (V) 7.5 5.0 2.5 0 -2.5 -5.0 -7.5 0 1000 2000 3000 4000 VOUTVOUT+
45 40 SUPPLY CURRENT (mA) 35 30 25 20 15 10 5 0
TRANSMITTER 1 AT DATA RATE TRANSMITTER 2 AT 1/16 DATA RATE
16
250kbps
120kbps
20kbps 2 0 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 LOAD CAPACITANCE (pF) LOAD CAPACITANCE (pF)
-10.0 5000 LOAD CAPACITANCE (pF)
4
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors
______________________________________________________________Pin Description
PIN 1 6 2 3 4 5 7 19 8 20 9 10 11, 12 13 14 15 16 17 18 NAME R2OUT R1OUT INVALID T2N T1IN FORCEON T1OUT T2OUT R1IN R2IN VCC FORCEOFF V+ C1+ C1C2+ C2VGND TTL/CMOS Receiver Outputs Invalid Signal Detector Output, active low. A logic high indicates that a valid RS-232 level is present on a receiver. TTL/CMOS Transmitter Outputs Force-On Input, active high. Drive high to override AutoShutdown Plus, keeping transmitters and receivers active (FORCEOFF must be high) (Table 1). RS-232 Transmitter Outputs RS-232 Receiver Outputs Supply Voltage (MAX3233E = +3.3V, MAX3235E = +5.0V) Force-Off Input, active low. Drive low to shut down transmitters, receivers, and charge pump. This overrides AutoShutdown Plus and FORCEON (Table 1). +5.5V generated by the charge pump. Do not connect. Positive terminal of the internal voltage-doubling charge-pump capacitor. Leave unconnected or connect to an external 0.1F capacitor. See Charge Pump Section. Negative terminal of the internal voltage-doubling charge-pump capacitor. Leave unconnected or connect to an external 0.1F capacitor. See Charge Pump Section. Positive terminal of the internal inverting charge-pump capacitor. Do not connect. Negative terminal of the internal inverting charge-pump capacitor. Do not connect. -5.5V generated by the charge pump. Do not connect. Ground FUNCTION
MAX3233E/MAX3235E
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3233E/MAX3235E'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), with no external capacitors. The charge pump operates in discontinuous mode: if the output voltages are less than 5.5V, the charge pump is enabled; if the output voltages exceed 5.5V, the charge pump is disabled.
POWERMANAGEMENT UNIT OR KEYBOARD CONTROLLER FORCEOFF FORCEON INVALID
MAX3233E MAX3235E
RS-232 Transmitters
The transmitters are inverting level translators that convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The devices guarantee a 250kbps data rate with worstcase 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. Figure 1 shows a complete system connection. When FORCEOFF is driven to ground or when the AutoShutdown Plus circuitry senses that all receiver and transmitter inputs are inactive for more than 30sec, the transmitters are disabled and the outputs go into a highimpedance state. When powered off or shut down, the outputs can be driven to 12V. The transmitter inputs do not have pull-up resistors. Connect unused inputs to GND or VCC.
I/O CHIP WITH UART RS-232
CPU
Figure 1. Interface Under Control of PMU
+0.3V
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic output levels. They feature inverting outputs that always remain active (Table 1). The MAX3233E/MAX3235E feature an INVALID output that is enabled low when no valid RS-232 voltage levels have been detected on all receiver inputs. Because INVALID indicates the receiver input's condition, it is independent of FORCEON and FORCEOFF states (Figures 2 and 3).
R_IN
-0.3V
80s TIMER R
INVALID
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 80s.
Figure 2a. INVALID Functional Diagram, INVALID Low
AutoShutdown Plus Mode
The devices achieve a 1A supply current with Maxim's AutoShutdown Plus feature, which operates when FORCEOFF is high and a FORCEON is low. When these devices do not sense a valid signal transition on any receiver or transmitter input for 30sec, 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 the UART driving the transmitter inputs is inactive. The system turns on again when a valid transition is
LapLink is a trademark of Traveling Software.
6
+2.7V
R_IN
-2.7V
80s TIMER R
INVALID
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN ABOVE +2.7V OR BELOW -2.7V FOR 1s.
Figure 2b. INVALID Functional Diagram, INVALID High
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
Table 1. Output Control Truth Table
OPERATION STATUS FORCEON FORCEOFF VALID RECEIVER LEVEL X X X X Yes X No Yes No Rx or Tx EDGE WITHIN 30sec X X Yes No X Yes No X X T_OUT R_OUT
Shutdown (Forced Off) Normal Operation (Forced On) Normal Operation (AutoShutdown Plus) Shutdown (AutoShutdown Plus) Normal Operation Normal Operation Shutdown Normal Operation (AutoShutdown) Shutdown (AutoShutdown)
X 1 0 0 INVALID* INVALID* INVALID* INVALID* INVALID*
0 1 1 1 1 1 1 INVALID** INVALID**
High-Z Active Active High-Z Active Active High-Z Active High-Z
Active Active Active Active Active Active Active Active Active
X = Don't care
* INVALID connected to FORCEON ** INVALID connected to FORCEON and FORCEOFF
EDGE DETECT
T_IN
FORCEOFF FORCEOFF S 30sec TIMER R AUTOSHDN* POWERDOWN*
R_IN
EDGE DETECT
FORCEON AUTOSHDN * POWERDOWN IS ONLY AN INTERNAL SIGNAL. IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES.
FORCEON *AUTOSHDN IS ONLY AN INTERNAL SIGNAL.
Figure 2c. AutoShutdown Plus Logic
Figure 2d. Power-Down Logic
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 depict invalid and valid RS-232 receiver voltage levels. INVALID indicates the receiver input's condition, and is independent of FORCEON and FORCEOFF states. Figure 2 and Tables 1 and 2 summarize the operating modes. FORCEON and FORCE-
OFF 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. When shut down, the device's charge pumps turn off, V+ is pulled to VCC, V- is pulled to ground, and the transmitter outputs are high impedance. The time required to exit shutdown is typically 100s (Figure 7).
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
By connecting FORCEON to INVALID, the device shuts down when no valid receiver level and no receiver or transmitter edge is detected for 30sec. It wakes up when a valid receiver level or receiver or transmitter edge is detected. By connecting FORCEON and FORCEOFF to INVALID, the device shuts down when no valid receiver level is detected and wakes up when a valid receiver level is detected. A system with AutoShutdown Plus may need time to wake up. Figure 4 shows a circuit that forces the transmitters on for 100ms, allowing enough time for another system to realize that the MAX3233E/ MAX3235E is awake. If another system outputs valid RS-232 signal transitions within that time, the RS-232 ports on both systems remain enabled.
Software-Controlled Shutdown
If direct software control is desired, use INVALID to indicate DTR or Ring Indicator signal. Tie FORCEOFF and FORCEON together to bypass the AutoShutdown Plus so the line acts like a SHDN input.
15kV ESD Protection
As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver outputs and receiver inputs have extra protection against static electricity. Maxim's engineers have developed state-of-the-art structures to protect these pins against ESD of 15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown, and powered down. After an ESD
INVALID HIGH +2.7 RECEIVER INPUT LEVELS (V) INDETERMINATE +0.3 0 -0.3 INDETERMINATE -2.7 INVALID HIGH INVALID LOW
Table 2. INVALID Truth Table
RS-232 SIGNAL PRESENT AT ANY RECEIVER INPUT Yes No INVALID OUTPUT High Low
Figure 3a. Receiver Positive/Negative Thresholds for INVALID
RECEIVER INPUTS
} REGION
INVALID
TRANSMITTER INPUTS
TRANSMITTER OUTPUTS VCC 0
INVALID OUTPUT
tINVL
tINVH tAUTOSHDN tWU
tAUTOSHDN tWU
V+ VCC 0 V-
Figure 3b. AutoShutdown Plus, INVALID, and READY Timing Diagram
8 _______________________________________________________________________________________
15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
POWERMANAGEMENT UNIT MASTER SHDN LINE 0.1F 1M
RC 50M to 100M CHARGE CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
FORCEOFF FORCEON
Cs 150pF STORAGE CAPACITOR
MAX3233E MAX3235E
Figure 4. AutoShutdown Plus Initial Turn-On to Wake Up Another System
Figure 6a. IEC 1000-4-2 ESD Test Model
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1500 DISCHARGE RESISTANCE DEVICE UNDER TEST
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
Cs 100pF
STORAGE CAPACITOR
ESD Test Conditions ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results.
Figure 5a. 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)
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 integrated circuits. The MAX3233E/MAX3235E help 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
9
tDL CURRENT WAVEFORM
Figure 5b. Human Body Current Waveform
event, Maxim's E versions keep working without latchup, whereas competing RS-232 products can latch and must be powered down to remove latchup.
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
I 100% 90% VCC VCC CBYPASS
I PEAK
MAX3233E MAX3235E
T_ IN 10% R_ OUT t r = 0.7ns to 1ns t 30ns 60ns VCC FORCEOFF GND FORCEON
T_ OUT
R_ IN 5k
1000pF
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
Figure 8. Loopback Test Circuit
5V/div 0 FORCEON = FORCEOFF T1OUT
manufacturing. Of course, 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.
2V/div 0
__________Applications Information
Charge Pumps
The MAX3233E/MAX3235E do not require external capacitors to operate their internal charge pumps. The MAX3235E can be operated down to 3.0V by paralleling the internal C1 capacitor with an external 0.1F. When using an external capacitor across the C1 terminals, check to confirm that the total supply voltage measured from V+ to V- does not exceed the absolute maximum voltage of 13V. With the external 0.1F capacitor added, the MAX3235E should not be used with a supply greater than +3.9V.
10V/div 0
VCC = 3.3V
T2OUT
10s/div
Figure 7. Transmitter Outputs when Exiting Shutdown or Powering Up
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 applications, a 0.1F VCC bypass capacitor is adequate. Connect bypass capacitors as close to the IC as possible.
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
10
Transmitter Outputs when Exiting 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).
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15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors
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. Figure 9, all transmitters were driven simultaneously at 120kbps into RS-232 loads in parallel with 1000pF. For Figure 10, a single transmitter was driven at 250kbps, and all transmitters were loaded with an RS-232 receiver in parallel with 250pF.
MAX3233E/MAX3235E
High Data Rates
The MAX3233E/MAX3235E maintain the RS-232 5.0V minimum transmitter output voltage even at high data rates. Figure 8 shows a transmitter loopback test circuit. Figure 9 shows a loopback test result at 120kbps, and Figure 10 shows the same test at 250kbps. For
Interconnection with 3V and 5V Logic
The MAX3233E/MAX3235E can directly interface with various 5V logic families, including ACT and HCT CMOS. See Table 3 for more information on possible combinations of interconnections.
T1IN
5V/div
T1IN
5V/div
5V/div T1OUT T1OUT
5V/div
R1OUT VCC = 3.3V (MAX3233E), VCC = 5.0V (MAX3235E) 2s/div
5V/div
R1OUT VCC = 3.3V (MAX3233E), VCC = 5.0V (MAX3235E) 2s/div
5V/div
Figure 9. Loopback Test Result at 120kbps
Figure 10. Loopback Test Result at 250kbps
Table 3. Logic Family Compatibility with Various Supply Voltages
DEVICE MAX3233E MAX3233E MAX3235E LOGIC POWER-SUPPLY VOLTAGE (V) 3.3 5 3.3/5 VCC SUPPLY VOLTAGE (V) 3.3 3.3 5 COMPATIBILITY Compatible with all CMOS families Compatible with ACT and HCT CMOS, and with AC, HC, or CD4000 CMOS Compatible with all TTL and CMOS families
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11
15kV ESD-Protected, 1A, 250kbps, 3.3V/5V, Dual RS-232 Transceivers with Internal Capacitors MAX3233E/MAX3235E
Typical Operating Circuit
VCC CBYPASS 0.1F 13 C1+ 14 C115 16 C2+ C2T1OUT 7 RS-232 OUTPUTS 9 VCC V+ 11, 12
Ordering Information (continued)
PART MAX3235ECWP MAX3235ECPP MAX3235EEWP MAX3235EEPP TEMP. RANGE 0C to +70C 0C to +70C -40C to +85C -40C to +85C PIN-PACKAGE 20 SO 20 Plastic DIP 20 SO 20 Plastic DIP
MAX3233E MAX3235E
V-
17
4 T1IN TTL/CMOS INPUTS
3 T2IN
T2OUT
19
6 R1OUT TTL/CMOS OUTPUTS 1 R2OUT 5k 5k
R1IN
8 RS-232 INPUTS
___________________Chip Information
TRANSISTOR COUNT: 1129
R2IN
20
AUTOSHUTDOWN PLUS
INVALID 2 FORCEOFF 10 FORCEON 5 VCC
GND 18
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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