DS275
Line-Powered RS-232 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
Ultra-low static current, even when connected
to RS-232-E port
Variable transmitter level from +5 to +12
volts
Compatible with RS-232-E signals
Available in 8-pin, 150 mil wide SOIC
package (DS275S)
Low-power CMOS
PIN ASSIGNMENT
RX
OUT
V
DRV
TX
IN
GND
1
2
3
4
8
7
6
5
V
CC
RX
IN
NC
TX
OUT
DS275 8-Pin DIP (300-mil)
DS275 8-Pin SOIC (150-mil)
RX
OUT
NC
V
DRV
NC
TX
IN
NC
GND
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V
CC
NC
NC
RX
IN
NC
NC
TX
OUT
ORDERING INFORMATION
DS275
DS275S
DS275E
8-pin DIP
8-pin SOIC
14-pin TSSOP
RX
OUT
V
DRV
TX
IN
GND
TX
OUT
NC
RX
IN
V
CC
DS275E 14-Pin TSSOP
PIN DESCRIPTION
- RS-232 Receiver Output
- Transmit driver +V
- RS-232 Driver Input
- System Ground (0V)
- RS-232 Driver Output
- No Connection
- RS-232 Receive Input
-System Logic Supply (+5V)
DESCRIPTION
The DS275 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 employs a unique circuit which steals current from the receive RS-
232 signal when that signal is in a negative state (marking). Since most serial communication ports
remain in a negative state statically, using the receive signal for negative power greatly reduces the
DS275’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 DS275’s transmitter will use system power (5-12 volts) for positive transitions while still
employing the receive signal for negative transitions.
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