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MAX3243E

MAX3243E
MAX3243E

General Description

The MAX3221E/MAX3223E/MAX3243E are 3V-powered EIA/TIA-232 and V.28/V.24 communications interfaces with automatic shutdown/wakeup 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 MAX3221E/MAX3223E/MAX3243E achieve a 1μA supply current with Maxim’s revolutionary AutoShutdown? feature. They save power without changes to the existing BIOS or operating system by enter-ing low-power shutdown mode when the RS-232 cable is disconnected, or when the transmitters of the connected peripherals are off.

The transceivers have a proprietary low-dropout trans-mitter output stage, delivering true RS-232 performance from a +3.0V to +5.5V supply with a dual charge pump.The charge pump requires only four small 0.1μF capaci-tors for operation from a +3.3V supply. Each device is guaranteed to run at data rates of 250kbps while main-taining RS-232 output levels.

The MAX3221E contains just one driver and one receiver,making it the smallest single-supply RS-232 transceiver.The MAX3223E has two drivers and two receivers. The MAX3243E is a complete 3-driver/5-receiver serial port ideal for notebook or subnotebook computers. It also includes two noninverting receiver outputs that are always active, allowing external devices to be monitored without forward biasing the protection diodes in circuitry that may be powered down.

The MAX3221E, MAX3223E, and MAX3243E are avail-able in space-saving SSOP packages.

Applications

Notebook, Subnotebook, and Palmtop Computers Cellular Phones

Battery-Powered Equipment Hand-Held Equipment Peripherals Printers

Features

o ESD Protection for RS-232 I/O Pins:

±15kV—Human Body Model

±8kV—IEC1000-4-2, Contact Discharge ±15kV—IEC1000-4-2, Air-Gap Discharge o Latchup Free o 1μA Supply Current

o 250kbps Guaranteed Data Rate o 6V/μs Guaranteed Slew Rate

o Meets EIA/TIA-232 Specifications Down to 3.0V o Smallest Single-Supply RS-232 Transceiver (MAX3221E)o Guaranteed Mouse Driveability (MAX3243E)o Small 0.1μF Capacitors

MAX3221E/MAX3223E/MAX3243E ?

±15kV ESD-Protected, 1μA, 3.0V to 5.5V , 250kbps,

RS-232 Transceivers with AutoShutdown

________________________________________________________________Maxim Integrated Products

1

19-1283; Rev 2; 1/98

AutoShutdown is a trademark of Maxim Integrated Products.

?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; 5,649,210; and other patents pending.

Pin Configurations appear at end of data sheet.Typical Operating Circuits appear at end of data sheet.

Selector Guide

For free samples & the latest literature: https://www.wendangku.net/doc/407871273.html,, or phone 1-800-998-8800.For small orders, phone 408-737-7600 ext. 3468.

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 2_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V CC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C.)

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.

V CC to GND..............................................................-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, EN , FORCEON, FORCEOFF to GND............-0.3V to +6V R_IN to GND......................................................................±25V Output Voltages

T_OUT to GND................................................................±13.2V R_OUT, R2OUTB, INVALID to GND.........-0.3V to (V CC + 0.3V)Short-Circuit Duration

T_OUT to GND.........................................................Continuous

Continuous Power Dissipation (T A = +70°C)

16-Pin SSOP (derate 7.14mW/°C above +70°C)...........571mW 20-Pin Plastic DIP (derate 11.11mW/°C above +70°C)....889mW 20-Pin SSOP (derate 8.00mW/°C above +70°C)...........640mW 28-Pin Wide SO (derate 12.50mW/°C above +70°C)............1W 28-Pin SSOP (derate 9.52mW/°C above +70°C)............762mW Operating Temperature Ranges

MAX32_ _EC_ _....................................................0°C to +70°C MAX32_ _EE_ _..................................................-40°C to +85°C Storage Temperature Range.............................-65°C to +160°C Lead Temperature (soldering, 10sec).............................+300°C

Note 1:V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.

MAX3221E/MAX3223E/MAX3243E

RS-232 Transceivers with AutoShutdown

_______________________________________________________________________________________3

ELECTRICAL CHARACTERISTICS (continued)

(V CC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C.)

Typical Operating Characteristics

(V CC = +3.3V, 250kbps data rate, 0.1μF capacitors, all transmitters loaded with 3k ?and C L , T A = +25°C, unless otherwise noted.)

-6

-5-4-3-2-101234560

1000

2000

3000

4000

5000

MAX3221E/MAX3223E

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

LOAD CAPACITANCE (pF)T R A N S M I T T E R O U T P U T V O L T A G E (V )

2

4

6810121416

1000

2000

3000

4000

5000

MAX3221E/MAX3223E

SLEW RATE vs. LOAD CAPACITANCE

LOAD CAPACITANCE (pF)

S L E W R A T E (V /μs )

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 4_______________________________________________________________________________________

TIMING CHARACTERISTICS—MAX3221E/MAX3223E/MAX3243E

(V CC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C.)

Note 2:C1–C4 = 0.1μF, tested at 3.3V ±10%. C1 = 0.047μF, C2–C4 = 0.33μF, tested at 5.0V ±10%.Note 3:Transmitter skew is measured at the transmitter zero cross points.

MAX3221E/MAX3223E/MAX3243E

RS-232 Transceivers with AutoShutdown

_______________________________________________________________________________________5

Typical Operating Characteristics (continued)

(V CC = +3.3V, 250kbps data rate, 0.1μF capacitors, all transmitters loaded with 3k ?and C L , T A = +25°C, unless otherwise noted.)

-6

-5-4-3-2-101234560

MAX3243E

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

LOAD CAPACITANCE (pF)

T R A N S M I T T E R O U T P U T V O L T A G E (V )

2000

3000

1000

40005000

42861210140

1000

2000

3000

4000

5000MAX3243E

SLEW RATE vs. LOAD CAPACITANCE

M A X 3243E -05

LOAD CAPACITANCE (pF)S L E W R A T E (V /μs

)

30

20104050600

2000

1000

3000

40005000

MAX3243E

OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE

LOAD CAPACITANCE (pF)

S U P P L Y C U R R E N T (m A )

51015202530

354045

2000

1000

3000

4000

5000

MAX3221E/MAX3223E OPERATING SUPPLY CURRENT vs. LOAD CAPACITANCE

LOAD CAPACITANCE (pF)

S U P P L Y C U R R E N T (m A )

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 6

_______________________________________________________________________________________

Pin Description

_______________Detailed Description

Dual Charge-Pump Voltage Converter

The MAX3221E/MAX3223E/MAX3243E’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), over the +3.0V to +5.5V V CC range. The charge pumps operate in 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.

RS-232 Transmitters

The transmitters are inverting level translators that con-vert CMOS-logic levels to 5.0V EIA/TIA-232 levels. They 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 LapLink?. Transmitters can be paralleled to drive mul-tiple receivers. The MAX3243E has been specifically designed to drive serial mice. Figure 1shows a com-plete system connection.

When FORCEOFF is driven to ground, or the AutoShutdown circuitry senses invalid voltage levels on all receiver inputs, the transmitters are disabled and the outputs are forced into a high-impedance state. When powered off or shut down, the output can be driven up to ±12V. The transmitter inputs do not have pull-up resistors.

LapLink is a trademark of Traveling Software.

MAX3221E/MAX3223E/MAX3243E

RS-232 Transceivers with AutoShutdown

_______________________________________________________________________________________7

RS-232 Receivers

The MAX3221E/MAX3223E/MAX3243E’s receivers con-vert RS-232 signals to CMOS-logic output levels. All receivers have inverting three-state outputs and can be active or inactive. In shutdown (FORCEOFF = low) or in AutoShutdown, the MAX3221E/MAX3223E’s receivers are active (Table 1). Drive EN high to place the receiv-er(s) in a high-impedance state. The MAX3243E’s receivers are high-impedance when the part is in shut-down (FORCEOFF = low).

The MAX3243E features an extra, always-active com-plementary output (R2OUTB). R2OUTB monitors receiver activity while the other receivers are high-impedance. This allows Ring Indicator to be monitored without forward biasing other devices connected to the receiver outputs. This is ideal for systems where V CC drops to 0 in shutdown to accommodate peripherals such as UARTs (Figure 2).

Figure 1. Interface Under Control of PMU

Figure 2. The MAX3243E detects RS-232 activity when the UART and interface are shut down.

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 8_______________________________________________________________________________________

Table 1. Output Control Truth Table

Figure 3a. MAX32_ _E Entering 1μA Supply Mode via

AutoShutdown Figure 3b. MAX32__E with Transmitters Enabled Using AutoShutdown

X = Don’t Care

The MAX3221E/MAX3223E/MAX3243E feature an INVALID output that is enabled low when no valid RS-232signal levels have been detected on all receiver inputs.INVALID is functional in any mode (Figures 3 and 5).

AutoShutdown

The MAX3221E/MAX3223E/MAX3243E achieve a 1μA supply current with Maxim’s new AutoShutdown fea-ture, which operates when FORCEON is low and FORCEOFF is high. When these devices sense no valid

signal levels on all receiver inputs for 30μs, the on-board charge pump and drivers are shut off, reducing supply current to 1μA. This occurs if the RS-232 cable is disconnected or the connected peripheral transmit-ters are turned off. The device turns on again when a valid level is applied to any RS-232 receiver input. As a result, the system saves power without changes to the existing BIOS or operating system.

MAX3221E/MAX3223E/MAX3243E

_______________________________________________________________________________________9

1μA Supply-Current, True +3V to +5.5V RS-232 Transceivers with AutoShutdown?

Table 2 and Figure 3c summarize the MAX3221E/MAX3223E/MAX3243E operating modes. FORCEON and FORCEOFF override AutoShutdown. When neither control is asserted, the IC selects between these states automatically, based on receiver input levels. Figures 3a, 3b, and 5a depict valid and invalid RS-232 receiver levels. Figure 5 shows the input levels and timing dia-gram for AutoShutdown operation.

A mouse or other system with AutoShutdown may need time to wake up. Figure 4shows a circuit that forces the transmitters on for 100ms, allowing enough time for the other system to realize that the MAX3221E/MAX3223E/MAX3243E are awake. If the other system transmits valid RS-232 signals within that time, the RS-232 ports on both systems remain enabled.

When shut down, the device’s charge pumps are off, V+is pulled to V CC , V- is pulled to ground, and the trans-mitter outputs are high impedance. The time required to exit shutdown is typically 100μs (Figure 5b).

Software-Controlled Shutdown

If direct software control is desired, INVALID can be used to indicate DTR or Ring Indicator signal. Connect FORCEOFF and FORCEON together to disable Auto-Shutdown so the line acts like a SHDN input.

Figure 5. AutoShutdown Trip Levels

Figure 4. AutoShutdown with Initial Turn-On to Wake Up a Mouse or Another System

FORCEOFF POWER DOWN

INVALID

FORCEON INVALID IS AN INTERNALLY GENERATED SIGNAL THAT IS USED BY THE AUTOSHUTDOWN LOGIC AND APPEARS AS AN OUTPUT OF THE DEVICE.POWER DOWN IS ONLY AN INTERNAL SIGNAL.IT CONTROLS THE OPERATIONAL STATUS OF THE TRANSMITTERS AND THE POWER SUPPLIES.

Figure 3c. MAX32_ _E AutoShutdown Logic

Table 2. INVALID Truth Table

Low

No

High Yes INVALID OUTPUT

RS-232 SIGNAL PRESENT AT ANY RECEIVER INPUT

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 10

______________________________________________________________________________________

±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 of the MAX3221E/MAX3223E/MAX3243E have extra protection against static electricity. Maxim’s engineers have devel-oped state-of-the-art structures to protect these pins against ESD of ±15kV without damage. The ESD struc-tures withstand high ESD in all states: normal operation,shutdown, and powered down. After an ESD event,Maxim’s E versions keep working without latchup, where-as competing RS-232 products can latch and must be powered down to remove latchup.

ESD protection can be tested in various ways; the trans-mitter 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 IEC1000-4-23) ±15kV using IEC1000-4-2’s air-gap method

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.

Human Body Model

Figure 6a shows the Human Body Model, and Figure 6b shows the current waveform it generates when dis-charged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of inter-est, which is then discharged into the test device through a 1.5k ?resistor.

IEC1000-4-2

The IEC1000-4-2 standard covers ESD testing and per-formance of finished equipment; it does not specifi-cally refer to integrated circuits. The MAX3221E/MAX3223E/MAX3243E help you design equipment that meets Level 4 (the highest level) of IEC1000-4-2, with-out the need for additional ESD-protection components.

Figure 7a. IEC1000-4-2 ESD Test Model

Figure 7b. IEC1000-4-2 ESD Generator Current Waveform

Figure 6a. Human Body ESD Test Models

Figure 6b. Human Body Model Current Waveform

The major difference between tests done using the Human Body Model and IEC1000-4-2 is higher peak current in IEC1000-4-2, because series resistance is lower in the IEC1000-4-2 model. Hence, the ESD with-stand voltage measured to IEC1000-4-2 is generally lower than that measured using the Human Body Model. Figure 7a shows the IEEE1000-4-2 model and Figure 7b shows the current waveform for the ±8kV IEC1000-4-2 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.

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 manufactur-ing. 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.

___________Applications Information

Capacitor Selection

The capacitor type used for C1–C4 is not critical for proper operation; either polarized or nonpolarized capacitors may be used. The charge pump requires 0.1μF capacitors for 3.3V operation. For other supply voltages, refer to Table 3for required capacitor values.Do not use values smaller than those listed in Table 3.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 exces-sively with temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s equivalent series resistance (ESR) usually rises at low temperatures and influences the amount of ripple on V+ and V-.

Power-Supply Decoupling

In most circumstances, a 0.1μF V CC bypass capacitor is adequate. In applications that are sensitive to power-supply noise, use a capacitor of the same value as the charge-pump capacitor C1. Connect bypass capacitors as close to the IC as possible.

Transmitter Outputs when Exiting Shutdown

Figure 8shows two transmitter outputs when exiting shut down mode. As they become active, the two trans-mitter outputs are shown going to opposite RS-232 lev-els (one transmitter output 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,and are enabled only when the magnitude of V-exceeds approximately -3V.

MAX3221E/MAX3223E/MAX3243E

RS-232 Transceivers with AutoShutdown

______________________________________________________________________________________

11

40μs/div

T2OUT

FORCEON =FORCEOFF T1OUT

5V/div

2V/div

V CC = 3.3V C1–C4 = 0.1μF

Figure 8. Transmitter Outputs Exiting Shutdown or Powering Up

M A X 3221E /M A X 3223E /M A X 3243E

High Data Rates

The MAX3221E/MAX3223E/MAX3243E maintain the RS-232 ±5.0V minimum transmitter output voltage even at high data rates. Figure 9 shows a transmitter loopback test circuit. Figure 10 shows a loopback test result at 120kbps, and Figure 11 shows the same test at 250kbps.For Figure 10, all three transmitters were driven simulta-neously at 120kbps into RS-232 loads in parallel with 1000pF. For Figure 11, a single transmitter was driven at 250kbps, and all three transmitters were loaded with an RS-232 receiver in parallel with 1000pF.

Mouse Driveability (MAX3243E)

The MAX3243E has been specifically designed to power serial mice while operating from low-voltage power sup-plies. It has been tested with leading mouse brands such as Logitech and Microsoft. When tested, the MAX3243E successfully drove all serial mice and met their respective current and voltage requirements. The MAX3243E’s regu-lated dual charge pump ensures the transmitters will sup-ply at least ±5V during worst-case conditions. Figure 12a shows the transmitter outputs under increasing load cur-rent. The AutoShutdown feature does not work with a mouse, so FORCEOFF and FORCEON should be con-nected to V CC . Figure 12b (on the following page) shows a mouse driver test circuit. To achieve mouse driveability with 1μA supply current when the port is inactive, use parts with the AutoShutdown Plus feature (such as the MAX3244E and MAX3245E).

RS-232 Transceivers with AutoShutdown 12

______________________________________________________________________________________

Figure 12a. Transmitter Output Voltage vs. Load Current per Transmitter

Figure 9. Loopback Test Circuit

2μs/div

V CC = 3.3V

Figure 11. Loopback Test Result at 250kbps

Figure 10. Loopback Test Result at 120kbps 2μs/div

T1IN T1OUT

R1OUT

5V/div

5V/div

5V/div

V CC = 3.3V

MAX3221E/MAX3223E/MAX3243E

RS-232 Transceivers with AutoShutdown

______________________________________________________________________________________

13

Figure 12b. Mouse Driver Test Circuit

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 14______________________________________________________________________________________

Table 5. ±15kV ESD-Protected, 3.0V to 5.5V Powered RS-232 Transceivers from Maxim

___________________Chip Information

MAX3221E

TRANSISTOR COUNT: 269

MAX3223E

TRANSISTOR COUNT: 339

MAX3243E

TRANSISTOR COUNT: 476

Interconnection with 3V and 5V Logic

The MAX3221E/MAX3223E/MAX3243E can directly inter-face with various 5V logic families, including ACT and

HCT CMOS. See Table 4 for more information on possi-ble combinations of interconnections.

MAX3221E/MAX3223E/MAX3243E

RS-232 Transceivers with AutoShutdown

Typical Operating Circuits

M A X 3221E /M A X 3223E /M A X 3243E

RS-232 Transceivers with AutoShutdown 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.

16____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600?1998 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

Pin Configurations

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