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RS-485 interface reference design for absolute encoders

This high EMC immunity reference design demonstrates a RS-485 transceiver to use on both the drive and within encoders such as: EnDat 2.2, BiSS, Tamagawa, etc. EMC immunity, particularly immunity against inverter switching noise, is important for position encoder feedback systems within industrial drives. This design supports a wide input voltage range (used as output voltage to the encoder) from 5 to 15V (12V nom) in order to meet the wide supply range of encoders.

Design

14 September 2018

byNews Desk

The power supply of this design includes protection against overvoltage and short circuit according to the selected encoder’s voltage range to prevent damage during a cable short.

The BoosterPack plug-in module form factor with connector compatible to TI LaunchPad development kit is included for easy evaluation of EnDat, BiSS, and other systems with the C2000 MCU. This reference design has been tested up to 100-m cable length with EnDat 2.2 encoders.

Features

5V, half-duplex RS-485 transceiver (THVD1550), 50-Mbaud, with 16-kV IEC-ESD and 4-kV EFT eliminates cost for external ESD components
Design achieves highest immunity within industry against IEC 61000-4-4 fast electrical transients
Supports 4-wire RS-485 interface standards such as EnDat2.2, BiSS or 2-wire interfaces standards such as Tamagawa
Hardware can be used as both a drive and an encoder interface due to configurable clock direction
Designed to meet IEC 61800-3 EMC immunity

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