Switchable, Integrated Termination Simplifies RS485 Networks
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
Editor's Contact Information
- Doug Dickinson