Analog Front End (AFE) for Merging Units and Multi-Function Protection Relays Reference Design


Design files


This solution addresses the front end needs of Merging Units where multiple measurement channels for current and voltage are required. This implementation is modular, allowing easy expansion of channels while at the same time keeping the connectivity to the processor minimal by using the SPI daisy chain feature in the TI's SAR ADC. Additionally, this solution is compact because the AFE not only integrates the front end circuitry for each channel, but also integrates a voltage reference with low temperature drift

  • Integrated AFE solution including PGA and reference
  • The solution enables high accuracy without calibration and lower temperature co-efficient (reduces variation in accuracy due to change in temperature)
  • Modular approach + minimal MCU connectivity overhead
  • Increase number of input channels by adding additional SAR ADCs
  • Using daisy chain concept, the same SPI interface is used to connect multiple SAR ADCs
  • Measurement capabilities for protection and metering leveraging the higher sampling rate on the ADC
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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.

TIDU540A.PDF (1768 K)

Reference design overview and verified performance test data

TIDRB82.PDF (1195 K)

Detailed schematic diagram for design layout and components

TIDRB83.PDF (105 K)

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

TIDRB84.PDF (658 K)

Detailed overview of design layout for component placement

TIDRB86.ZIP (2103 K)

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

TIDC697.ZIP (339 K)

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

TIDRB85.PDF (208 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

Linear & low-dropout (LDO) regulators

TPS709150-mA, 30-V, ultra-low-IQ, low-dropout voltage regulator with reverse current protection and enable

Data sheet: PDF | HTML
Precision ADCs

ADS868816-bit, 500-kSPS, 8-channel, single-supply SAR ADC with bipolar input ranges

Data sheet: PDF | HTML

Technical documentation

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Type Title Date
* Design guide High-Accuracy AC Voltage and Current Measurement AFE for FTU Ref Design (Rev. A) Oct. 13, 2016

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