3V RS562 or 5V/3V RS232 Transceiver with One Receiver Active in Shutdown

The LT1331 is a 3-driver, 5-receiver RS232 transceiver designed for 3V and mixed 3V/5V systems. Receivers operate from 3V logic supply VL, while the onboard charge pump and drivers operate from 5V or 3V supply VCC.

The transceiver has two shutdown modes. One mode disables the drivers and the charge pump, the other shuts down all circuitry except for one low power receiver which can be used for ring detection. The VCC supply may be shut down while in ring detection mode. While shut down, the drivers and receivers assume high impedance output states.

The LT1331 is fully compliant with all EIA-RS232 specifications when VCC = 5V. If VCC = 3V, output drive levels are compatible with all known interface circuits. Special bipolar construction techniques protect the drivers and receivers beyond the fault conditions stipulated for RS232. The RS232 I/O pins are resilient to multiple ±10kV ESD strikes. An advanced driver output stage operates up to 120kbaud while driving heavy capacitive loads.

Applications

* Notebook Computers

* Palmtop Computers

* RS232 Compatible 3V Operation

* 3V Logic Interface

* ESD Protection Over ±10kV

* 120kbaud Operation for RL = 3k, CL = 2500pF

* 250kbaud Operation for RL = 3k, CL = 1000pF

* One Low Power Receiver Remains Active While in Shutdown

* 60µA Supply Current in Shutdown

* Low Power Driver Disable Mode

* Uses Small Capacitors: 0.1µF, 0.2µF

* CMOS Comparable Low Power: 60mW

* Easy PC Layout: Flowthrough Architecture

* Rugged Bipolar Design

* Outputs Assume a High Impedance State When Off or Powered Down