20Mbps RS485 Transceivers with Integrated Switchable Termination

The LTC2859 and LTC2861 are low power, 20Mbps RS485/422 transceivers operating on 5V supplies. The receiver includes a logic-selectable 120Ω termination, one-eighth unit load supporting up to 256 nodes per bus, and a fail-safe feature that guarantees a high output state under conditions of floating or shorted inputs.

The driver features a logic-selectable low-EMI 250kbps operating mode, and maintains a high output impedance over the entire common mode range when disabled or when the supply is removed. Excessive power dissipation caused by bus contention or a fault is prevented by current limiting all outputs and by a thermal shutdown.

Enhanced ESD protection allows the LTC2859 and LTC2861 to withstand ±15kV (human body model) on the transceiver interface pins without latch-up or damage.

Applications

* Low Power RS485/RS422 Transceiver

* Level Translator

* Backplane Transceiver

* Integrated, Logic-Selectable 120Ω Termination Resistor

* 20Mbps Max Data Rate

* No Damage or Latch-up to ESD: ±15kV HBM

* High Input Impedance Supports 256 Nodes

* 250kbps Low-EMI Mode

* Guaranteed Fail-safe Receiver Operation Over the Entire Common Mode Range

* Current Limited Drivers and Thermal Shutdown

* Delayed Micropower Shutdown (5μA Max)

* Power Up/Down Glitch-Free Driver Outputs

* Low Operating Current (900μA Max in Receive Mode)

* Meets All TIA/EIA-485-A Specifications

* Available in 10-Pin 3mm × 3mm DFN, 12-Pin 4mm × 3mm DFN and 16-Pin SSOP Packages