Switchable, Integrated Termination Simplifies RS485 Networks

Mar 9 2006 -MILPITAS, CA
  • Linear Technology Corporation introduces the LTC2859 and LTC2861, half-duplex and full-duplex RS485 transceivers with switchable, integrated termination. Traditional RS485 networks require 120-Ohm termination resistors to be installed by the end user based on the physical layout of the twisted-pair wires and the placement of the nodes. As the bus is extended, the termination must be changed again by the end user. Switching the integrated termination in the LTC2859/LTC2861 on or off under software control allows the proper nodes to be terminated without the end user's physical intervention.


    In addition to the innovative termination capacity, the LTC2859/LTC2861 offer advanced transceiver features for industrial, medical and automotive applications. A slew rate control pin allows data rates up to 20Mbps or a low-EMI mode at 250kbps. The bus pin protection exceeds ±15kV for ESD strikes (Human Body Model). The receiver input impedance allows up to 256 nodes on a single bus. These features provide more functionality than existing RS485 transceivers and the integrated termination combined with the tiny DFN package provide a smaller solution overall.


    Specified over the commercial and industrial temperature ranges, the LTC2859 is offered in the 10-lead (3mm × 3mm) DFN package and the LTC2861 is offered in the 12-lead (4mm × 3mm) DFN and 16-lead SSOP packages. Pricing begins at $1.55 each in 1,000-piece quantities.


    Summary of Features: LTC2859/LTC2861


    • Integrated, Logic-Selectable 120Ω Termination Resistor
    • No Damage or Latchup to ESD: ±15kV HBM
    • 20Mbps Max Data Rate
    • 250kbps Low-EMI Mode
    • High Input Impedance Supports 256 Nodes
    • Guaranteed Fail safe Receiver Operation Over the Entire Common Mode Range
    • Available in 10-Pin 3mm × 3mm DFN, 12-Pin 4mm × 3mm DFN and 16-Pin SSOP Packages

    RS485 with Integrated Termination

    LTC2859 PR Image

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