RS232/RS485 Multiprotocol Transceivers with Integrated Termination

The LTC2870/LTC2871 are robust pin-configurable multiprotocol transceivers, supporting RS232, RS485, and RS422 protocols, operating on a single 3V to 5.5V supply. The LTC2870 can be configured as two RS232 single-ended transceivers or one RS485 differential transceiver on shared I/O lines. The LTC2871 offers independent control of two RS232 transceivers and one RS485 transceiver, each on dedicated I/O lines.

Pin-controlled integrated termination resistors allow for easy interface reconfiguration, eliminating external resistors and control relays. Half-duplex switches allow four-wire and two-wire RS485 configurations. Loopback mode steers the driver inputs to the receiver outputs for diagnostic self-test.The RS485 receivers support up to 256 nodes per bus, and feature full failsafe operation for floating, shorted or terminated inputs.

An integrated DC/DC boost converter uses a tiny 2mm × 1.6mm inductor and one capacitor, eliminating the need for multiple supplies for driving RS232 levels.

Applications

* Software Selectable RS232/RS485/RS422 Interface

* Point-of-Sale Terminals

* Cable Repeaters

* Protocol Translators

* One RS485 and Two RS232 Transceivers

* 3V to 5.5V Supply Voltage

* 20Mbps RS485 and 500kbps RS232

* Automatic Selection of Integrated RS485 (120Ω) and RS232 (5kΩ) Termination Resistors

* Half-/Full-Duplex RS485 Switching

* High ESD: ±26kV (LTC2870), ±16kV (LTC2871)* Logic Loopback Mode