Reference Design for an Interface to a Position Encoder with EnDat 2.2


Design files


This reference design implements a hardware interface 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 eFuse technology and robust half-duplex RS-485 transceivers including line termination and EMC protection. An auxiliary power supply and logic level interface with adjustable I/O voltage level are 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.

  • Design meets EMC immunity requirements for ESD, fast-transient burst and surge according to IEC61800-3
  • High-speed RS-485 transceivers robust to 15-kV ESD immunity
  • Wide input (15 to 30 VDC) high-efficiency (>85%) DC/DC power supply configurable from 3.6 V to 14 V (defaulted to 8 V) with 200 mA, low-ripple (<20 mVpp) output
  • 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 3.3 V, 2.5 V or 1.8 V I/O interface to processors like Sitara AM4x for EnDat 2.2 master
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A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products

Design files

Download ready-to-use system files to speed your design process.

TIDU368.PDF (7780 K)

Reference design overview and verified performance test data

TIDR763.PDF (198 K)

Detailed schematic diagram for design layout and components

TIDR764.PDF (209 K)

Complete listing of design components, reference designators, and manufacturers/part numbers

TIDR765.PDF (130 K)

Detailed overview of design layout for component placement

TIDR766.ZIP (2340 K)

Files used for 3D models or 2D drawings of IC components

TIDC478.ZIP (185 K)

Design file that contains information on physical board layer of design PCB


Includes TI products in the design and potential alternatives.

RS-485 & RS-422 transceivers

SN65HVD783.3 V Half-Duplex RS-485, with IEC ESD, 50 Mbps

Data sheet: PDF | HTML
AC/DC & DC/DC converters (integrated FET)

TPS54040A3.5V to 42V Input, 0.5A Step-Down Converter with Eco-Mode

Data sheet: PDF | HTML
Direction-controlled voltage translators

SN74AVC8T2458-Bit Dual-Supply Bus Transceiver with Configurable Voltage-Level Shifting and 3-State Outputs

Data sheet: PDF | HTML
Linear & low-dropout (LDO) regulators

TLV700200-mA, high-PSRR, low-IQ, low-dropout voltage regulator with enable

Data sheet: PDF | HTML
Power modules (integrated inductor)

LMZ14201SIMPLE SWITCHER® 6V to 42V, 1A Power Module in Leaded Surface Mount TO Package

Data sheet: PDF | HTML
eFuses & hot swap controllers

TPS247502.5-V to 18-V, 3mΩ, 0.01-12A eFuse with driver for external blocking FET and latch off

Data sheet: PDF | HTML

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Technical documentation

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Type Title Date
* Design guide Interface to EnDat 2.2 Position Encoder Design Guide May 28, 2014
Technical article Designing an EMC-compliant interface to motor position encoders – Part 6 PDF | HTML Nov. 20, 2015
Technical article Designing an EMC-compliant interface to motor position encoders – Part 3 PDF | HTML Sep. 14, 2015

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