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112299

FEATURES

Low-power serial transmitter/receiver for

battery-backed systems

Transmitter steals power from receive signal

line to save power

Single 3V or 5V operation

Full duplex operation up to 20k bps

Ultra-low static current

Compatible with RS-232-E signals

PIN ASSIGNMENT

PIN DESCRIPTION

RS-232 Receiver Output

Transmit Driver Positive Supply

RS-232 Driver Input

GND

System Ground (0V)

RS-232 Driver Output

Transmit Driver Negative Supply

RS-232 Receiver Input

System Logic Supply (3-5V)

ORDERING INFORMATION

DS276

8-Pin DIP

DS276S

8-Pin SOIC

DESCRIPTION

The DS276 Line-Powered RS-232 Transceiver Chip is a CMOS device that provides a low-cost, very

low-power interface to RS-232 serial ports. The receiver input translates RS-232 signal levels to common

CMOS/TTL levels. The transmitter can be used with independently supplied positive and negative

supplies, but in most cases will be used with the positive supply, sharing the logic supply and the negative

supply stolen from the receive RS-232 signal when that signal is in a negative state (marking). By using

an external reservoir capacitor and Schottky diode (see Figure 4) this negative supply can be maintained

even during full-duplex operation. Since most serial communication ports remain in a negative state

statically, using the receive signal for negative power greatly reduces the DS276’s static power

consumption. This feature is especially important for battery-powered systems such as laptop computers,

remote sensors, and portable medical instruments. During an actual communication session, the DS276’s

transmitter will use system power (3-12 volts) for positive transitions while still employing the receive

signal for negative transitions.

DS276

Low Power Transceiver Chip

www.dalsemi.com

DS276 8-Pin DIP (300-mil)

DS 276S 8-Pin SOIC (150-mil)

GND

1

2

3

4

8

7

6

5