Reference design for an interface to a position encoder with EnDat 2.2

This TI Design implements a hardware interface solution based on the HEIDENHAIN EnDat 2.2 standard for position or rotary encoders. The building blocks include the power supply for the encoder – with innovative smart e-Fuse technology – and robust half-duplex RS485 transceivers, including line termination and EMC protection. An auxiliary power supply and logic level interface with adjustable I/O voltage level is provided to connect to subsequent MCUs and MPUs that would run the EnDat 2.2 Master protocol stack. This design is fully tested to meet EMC immunity requirements for ESD, Fast Transient Burst and Surge according to IEC61800-3. 

Features

• Design meets EMC immunity requirements for ESD, Fast Transient Burst and Surge according to IEC61800-3
• High-speed RS-485 transceivers robust to 15kV ESD immunity
• Wide input (15-30VDC) high-efficiency (>85%) DCDC power supply configurable from 3.6V to 14V (defaulted to 8V) with 200mA, low-ripple (
• Protected power supply with innovative eFuse technology to protect against over-current, over-power, over- and under-voltage and disconnect in case of fault.
• Option to shut down encoder power supply in case of fault or to save power when no encoder is connected.
• Level shifter to support 3.3V, 2.5V or 1.8V I/O interface to processors like Sitara AM4x for EnDat 2.2 Master.

Parts Include:

LMZ14201         SIMPLE SWITCHER® 6V to 42V, 1A Power Module in Leaded Surface Mount TO Package
SN65HVD78      3.3V, Half-Duplex RS-485, 12kV IEC ESD, 50Mbps data rate 
SN74AVC8T245 8-Bit Dual-Supply Bus Transceiver with Configurable Voltage-Level Shifting and 3-State Outputs 
TLV700              200mA, Low IQ, Low Dropout Regulator for Portables 
TPS24750          18V, 12A, 3mΩ eFuse with IMON and PG 
TPS54040A        3.5V to 42V Input, 0.5A Step-Down Converter with Eco-Mode 

Learn more by downloading the reference design below