DS276
Low Power Transceiver Chip
www.dalsemi.com
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
RX
OUT
V
DRV+
TX
IN
GND
1
2
3
4
8
7
6
5
V
CC
RX
IN
V
DRV-
TX
OUT
DS276 8-Pin DIP (300-mil)
DS 276S 8-Pin SOIC (150-mil)
PIN DESCRIPTION
RX
OUT
V
DRV+
TX
IN
GND
TX
OUT
V
DRV-
RX
IN
V
CC
RS-232 Receiver Output
Transmit Driver Positive Supply
RS-232 Driver Input
System Ground (0V)
RS-232 Driver Output
Transmit Driver Negative Supply
RS-232 Receiver Input
System Logic Supply (3-5V)
ORDERING INFORMATION
DS276
DS276S
8-Pin DIP
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.
1 of 11
112299
DALLAS [ DALLAS SEMICONDUCTOR ]
