DS1275

The DS1275 has the following features including Law-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-232-0 port;Variable transmitter level from +5 to +12 volts;Compatble with RS-232-0 signals;Available in 8-pin, 150-mil wide SOIL package(DS72753);Low-power CMOS.

The DS7275 Vrre-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 powergreatly reduces the DS1275's static power consumption. This feature is especially important for battery-powered systems such as laptop computers, remote sensors, and portable mescal instruments. During an actual communication session, the DS1275's transmitter wig use system power (5-12 voRs) for positive transitions while still employing the receive signal for negative transitions.

Designed  for  the  unique  requiremeris  of  battery-backed systems, the DS1275 provides a low-pow-er half-duplex interface to an RS-232 serial port.Typically a designermustusean RS-232 device which uses system power during both negative and posdive transitions of the transmit signal to the RS-232 port. If the connector to the RS-232 port is left connected for an appreciable time after the communication session has ended,power wdl statically flow into that port, draining the battery caipacity.The DS1275 eliminates this static current drain by stealling current from the receive line (RXin) of the RS-232 port when that line is at a negative level (marking). Since moat asynchronous commuover an RS-232 connection typically remains in a marking state when data is not being sent, the DS1275 will not consume system power in this condition. System power would only be used when positive-going transitions are needed on the transmit RS-232 output (TXout) when data is sent. However, since synchronous communication sessions typically exhibit a very low duty-cycle, overall system power consumption remains low.