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_______________General Description

The MAX3238 true RS-232 transceiver achieves a

1µA supply current with Maxim’s revolutionary

AutoShutdown Plus™ feature. When the device does

not sense a valid signal transition on either the receiver

or transmitter inputs within 30sec, the on-board power

supply and drivers shut down. This occurs if the RS-232

cable is disconnected or if the transmitters of the con-

nected peripheral are inactive. The system turns on

again when a valid transition is applied to any RS-232

receiver or transmitter input, saving power without

changes to the existing BIOS or operating system.

The MAX3238 5-driver/3-receiver complete serial port is

a 3V-powered EIA/TIA-232 and V.28/V.24 communica-

tions interface intended for notebook or subnotebook

computer applications. A proprietary, high-efficiency,

dual charge-pump power supply and a low-dropout

transmitter combine to deliver true RS-232 performance

from a single +3.0V to +5.5V supply. A guaranteed

data rate of 250kbps provides compatibility with popu-

lar software for communicating with personal comput-

ers. The MAX3238 requires only 0.1µF capacitors in

3.3V operation. It is ideal for 3.3V-only systems, mixed

3.3V and 5.0V systems, or 5V-only systems that require

true RS-232 performance.

Receiver R1 has an extra, always-active output (in addi-

tion to its standard output), which allows external

devices, such as a modem, to be monitored without for-

ward biasing the protection diodes in circuitry that may

have V

completely removed.

The MAX3238 is available in a space-saving SSOP

package.

________________________Applications

Notebook, Subnotebook, and Palmtop

Computers

High-Speed Modems

Battery-Powered Equipment

Hand-Held Equipment

Peripherals

Printers

AutoShutdown Plus

s a trademark of Maxim Integrated Products.

____________________________Features

♦ 1µA Supply Current Achieved with

AutoShutdown Plus

♦ Guaranteed Data Rate: 250kbps

♦ 1µA Low-Power Shutdown

♦ Receivers Active in AutoShutdown Plus Mode

♦ Flow-Through Pinout

♦ Meets EIA/TIA-232 Specifications Down to 3.0V

♦ Guaranteed 6V/µs Slew Rate

MAX3238

+3.0V to +5.5V, 1µA, up to 250kbps, True

RS-232 Transceiver with AutoShutdown Plus

________________________________________________________________ Maxim Integrated Products 1

C1+

V+

C1-

T1IN

T2IN

INVALID

T3IN

R1OUT

R2OUT

T4IN

R3OUT

T5IN

R1OUTB

FORCEOFF

FORCEON

T5OUT

R3IN

T4OUT

R2IN

R1IN

T3OUT

T2OUT

T1OUT

V-

C2-

GND

C2+

SSOP

TOP VIEW

MAX3238

__________________Pin Configuration

19-1144; Rev 1; 10/02

PART

MAX3238CAI

MAX3238EAI -40°C to +85°C

0°C to +70°C

TEMP RANGE PIN-PACKAGE

28 SSOP

______________Ordering Information

Typical Operating Circuit appears at end of data sheet.

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.

Summary of content (12 pages)

PAGE 1
9-1144; Rev 1; 10/02 +3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus Receiver R1 has an extra, always-active output (in addition to its standard output), which allows external devices, such as a modem, to be monitored without forward biasing the protection diodes in circuitry that may have VCC completely removed. The MAX3238 is available in a space-saving SSOP package.
PAGE 2
MAX3238 +3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus ABSOLUTE MAXIMUM RATINGS VCC ...........................................................................-0.3V to +6V V+ (Note 1) ...............................................................-0.3V to +7V V- (Note 1) ................................................................+0.3V to -7V V+ + |V-| (Note 1) .................................................................
PAGE 3
+3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus (V CC = +3.0V to +5.5V; C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF and C2–C4 = 0.33µF (tested at 5.0V ±10%); TA = TMIN to TMAX; unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS AutoShutdown (FORCEON = GND, FORCEOFF = VCC) Positive threshold 2.
PAGE 4
__________________________________________Typical Operating Characteristics (VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.) FOR DATA RATES UP TO 250kbps 1 TRANSMITTER 250kbps 4 TRANSMITTERS 15.6kbps LOADED 3kΩ + CL -2.5 +SLEW 10 8 1 TRANSMITTER 250kbps 4 TRANSMITTERS 15.6kbps LOADED 3kΩ + CL 6 60 SUPPLY CURRENT (mA) 2.5 –SLEW 12 70 MAX3238-02 5.0 0 14 MAX3238 TOC-01 VOUT+ SLEW RATE (V/µs) 7.5 SUPPLY CURRENT vs.
PAGE 5
+3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus MAX3238 Table 1.
PAGE 6
MAX3238 +3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus POWER MANAGEMENT UNIT OR KEYBOARD CONTROLLER VCC FORCEOFF FORCEON INVALID PROTECTION DIODE MAX3238 PREVIOUS RS-232 VCC I Rx T1 5kΩ UART T2 Tx T3 CPU I/O CHIP WITH UART GND SHDN = GND T4 RS-232 T5 (a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE RECEIVER OUTPUT IN SHUTDOWN. R1 VCC R2 TO µP R3 LOGIC TRANSITION DETECTOR I PROTECTION DIODE Figure 1.
PAGE 7
+3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus MAX3238 Table 2. INVALID Truth Table +0.3V RS-232 SIGNAL PRESENT AT ANY RECEIVER INPUT INVALID OUTPUT Yes H No L R_IN 30µs TIMER R -0.3V INVALID INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs. Figure 3a. INVALID Functional Diagram, INVALID Low Tables 1 and 2 and Figure 3 summarize the MAX3238’s operating modes.
PAGE 8
MAX3238 +3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus 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-. INVALID HIGH RECEIVER INPUT LEVELS +2.7V INDETERMINATE +0.3V 0V Table 3.
PAGE 9
+3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus Transmitter Outputs when Exiting Shutdown Figure 5 shows two transmitter outputs when exiting shutdown mode. As they become active, the outputs are shown going to opposite RS-232 levels (one transmitter input is high, the other is low). Each transmitter is loaded with 3kΩ in parallel with 2500pF. The transmitter outputs display no ringing or undesirable transients as they come out of shutdown.
PAGE 10
MAX3238 +3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus 5V 0V T1IN 5V 0V T1IN +5V +5V 0V T1OUT T1OUT 0V -5V -5V 5V 0V 5V R1OUT 0V VCC = 3.3V C1 - C4 = 0.1µF CLOAD = 1000pF 2µs/div Figure 7. Loopback Test Result at 120kbps R1OUT VCC = 3.3V C1 - C4 = 0.1µF CLOAD = 1000pF 2µs/div Figure 8.
PAGE 11
+3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus MAX3238 __________Typical Operating Circuit 0.1µF 26 VCC 28 C1+ 0.1µF V+ 27 * 0.1µF 25 C1- MAX3238 1 C2+ 0.1µF V- 4 0.
PAGE 12
MAX3238 +3.0V to +5.5V, 1µA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) DIM α E H C L A A1 B C D E e H L α INCHES MILLIMETERS MIN MAX MIN MAX 0.068 0.078 1.73 1.99 0.002 0.008 0.05 0.21 0.010 0.015 0.25 0.38 0.004 0.008 0.09 0.20 SEE VARIATIONS 0.205 0.209 5.20 5.38 0.0256 BSC 0.65 BSC 0.