Datasheet

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General Description

The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated

EIA/TIA-232 and V.28/V.24 communications interface

with high data-rate capabilities. The MAX3250 is a dual

die part that operates with up to ±50V difference

between the RS-232 side and the logic side (ISOCOM

to GND). This makes the device ideal for operation in

noisy conditions with high common-mode voltages.

This feature prevents damage to the device if RS-232

lines are inadvertently short-circuited to a +24V or ±48V

power bus.

The MAX3250 is powered by a single 3V to 5.5V supply

on the logic side. Power is transferred from the logic

side to the isolated side by ±100V external capacitors.

The MAX3250 has two receivers (Rx) and two drivers

(Tx) and is guaranteed to run at data rates of 250kbps

while maintaining RS-232 output levels. The trans-

ceivers have a proprietary low-dropout transmitter out-

put stage, delivering true RS-232 performance from a

3V to 5.5V supply with a dual charge pump. The device

features a FAULT open-drain output to signal an exces-

sive isolated-side voltage condition on any of the RS-

232 inputs. This output can drive an alarm LED or can

be monitored by the processor to prevent operation

under these conditions. The receiver outputs are high

impedance in shutdown, allowing multiple interfaces

(IrDA, RS-232, RS-485) to be connected to the same

UART.

The MAX3250 is available in a space-saving 28-pin

SSOP package.

Applications

Industrial Control

Programmable Logic Controller

Point-of-Sale Equipment

PC-to-Router Connections

Diagnostic Ports

Telecom Equipment

Features

o ±50V Isolation

o 20µA Supply Current in Shutdown

o 250kbps Guaranteed Data Rate

o FAULT Output

o High-Impedance Transmitter and Receiver

Outputs in Shutdown

o Space-Saving SSOP Package

o Inductorless/Transformerless Design Simplifies

EMI Compliance

o Low-Cost Replacement for Opto-Isolated

Transceivers

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

MAX3250

±50V Isolated, 3.0V to 5.5V,

250kbps, 2 Tx/2 Rx, RS-232 Transceiver

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-2443; Rev 3; 9/11

For pricing delivery, and ordering information please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Typical Operating Circuit appears at end of data sheet.

PART TEMP RANGE PIN-PACKAGE

MAX3250CAI+ 0°C to +70°C 28 SSOP

MAX3250EAI+ -40°C to +85°C 28 SSOP

C2-

GND

FAULT

SHDN

N.C.

ISOCOM

N.C.

C2+

ISOVCC

R1IN

R2IN

T1OUT

T2OUT

V-

C4-

C4+

C3-

V+

C3+

C1+

N.C.

T2IN

T1IN

R2OUT

R1OUT

C1-

SSOP

TOP VIEW

MAX3250

Pin Configuration

Denotes a lead(Pb)-free/RoHS-compliant package.

Summary of content (10 pages)

PAGE 1
9-2443; Rev 3; 9/11 ±50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities. The MAX3250 is a dual die part that operates with up to ±50V difference between the RS-232 side and the logic side (ISOCOM to GND). This makes the device ideal for operation in noisy conditions with high common-mode voltages.
PAGE 2
MAX3250 ±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver ABSOLUTE MAXIMUM RATINGS C1+, C2+, C3+, C3-, C4+, C4(All voltages referenced to GND, unless otherwise noted.) to ISOCOM .....................................-0.3V to (ISOVCC + 0.3V) VCC ...........................................................................-0.3V to +6V ISOCOM...............................................................................±80V T_OUT Current ..............
PAGE 3
±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver (VCC = 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25°C.) (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS +25 V RECEIVER INPUTS (relative to ISOCOM) Input-Voltage Range -25 Input Threshold Low TA = +25°C Input Threshold High TA = +25°C VCC = 3.3V 1.2 0.6 VCC = 5.0V 1.3 0.8 VCC = 3.3V 2.
PAGE 4
Typical Operating Characteristics (VCC = 3.3V, 250kbps data rate, see Typical Operating Circuit and Table 1 for capacitor values, all transmitters loaded with 3kΩ and CL to ISOCOM, TA = +25°C, unless otherwise noted.) SLEW RATE vs.
PAGE 5
±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver PIN NAME FUNCTION Negative Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C1- to C1+. See Table 1 for values. 1 C1- 2 R1OUT 3 R2OUT TTL/CMOS Receiver Output 4 T1IN TTL/CMOS Transmitter Input TTL/CMOS Receiver Output 5 T2IN TTL/CMOS Transmitter Input 6, 22, 23 N.C. No Connection. Not internally connected. 7 N.C. No Connection. Leave unconnected or connect to ISOCOM.
PAGE 6
MAX3250 ±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver TIN1 TOUT1 RIN1 ROUT1 TIN2 TOUT2 ROUT2 RIN2 SHDN ISOVCC FAULT OSC V+ MAX3250 RS-232 CHARGE PUMP VCC POWER CONTROLLER FAULT DETECTOR GND C1- C2- C1+ C2+ C3+ C3C4+ C4V- ISOCOM Figure 1. Functional Diagram Detailed Description The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities.
PAGE 7
±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver Dual Charge-Pump Voltage Converter The RS-232 drivers are powered from a regulated dual charge pump that provides output voltages of +5.5V (doubling charge pump) and -5.5V (inverting charge pump) relative to ISOCOM over the 3.0V to 5.5V VCC range. The charge pumps are powered from ISOVCC and 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.
PAGE 8
MAX3250 ±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver Table 1. Required Capacitor Values C1, C2 (µF) C3 (µF) C4, C7, C8 (µF) C5 (µF) C6 (µF) C9 (nF) 3.0 to 3.6 0.47 0.1 0.47 1 2.2 10 4.5 to 5.5 0.047 0.1 0.47 1 2.2 10 VCC (V) To achieve full isolation capability, C1, C2, and C9 should be rated for 100V or higher operation and be X7R or X5R type or metalized film dielectric.
PAGE 9
±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver REMOTE XCVR VCC C5 1µF CABLE VCC REMOTE MICRO RIN1 TOUT1 FAULT RIN2 MICRO SHDN TIN1 ROUT1 TIN2 ROUT2 C1 0.47µF C2 0.47µF TOUT2 C4+ MAX3250 C4 0.47µF C4C3+ C3 0.1µF C3V+ C1+ C1C2+ VISOVCC C6 2.2µF C2GND C8 0.47µF C7 0.47µF ISOCOM C9 10nF ±50V GND OFFSET Package Information Chip Information PROCESS: BiCMOS REMOTE GROUND For the latest package outline information and land patterns (footprints), go to www.maxim-ic.
PAGE 10
MAX3250 ±50V Isolated, 3.0V to 5.5V, 250kbps, 2 TX/2 RX, RS-232 Transceiver Revision History REVISION NUMBER REVISION DATE 0 4/02 Initial release — 1 2/03 Updated Design — 2 1/08 Updated EC table 3 3 9/11 Added lead-free packaging information; corrected pin names, power dissipation, and soldering temperature in Absolute Maximum Ratings; updated capacitor values in data sheet.