High Resolution, Fast Startup Analog Front End for Air Circuit Breaker Reference Design


Design files


The TIDA-00661 reference design features signal processing front-end subsystem for electronic trip units (ETU) used in air circuit breakers (ACB) or molded case circuit breakers (MCCB). This subsystem consists of Delta-Sigma ADC with 24-Bit resolution and fast startup (< 3ms), ±2.5V regulator, FRAM-based microcontroller (MCU) for interfacing to ADC and processing the inputs. The subsystem is designed to start-up, compute full-cycle RMS current, make decisions, and provide trip signal to the solenoid within 30 ms.

  • Measurement of AC input from 10V to 750V and 50mA to 25A within ±1% with fixed gain
  • Voltage and Current inputs are interfaced to a 24-Bit Delta-Sigma ADC with Fast startup (< 3ms)
  • DC-DC converters configured in Fly-Buck configuration to generate supply output (2W/ 8W)
  • Provides option to measure 3 earth fault current inputs with a single gain opamp interfaced to 12-Bit internal ADC of MCU
  • On-Board potential divider provided to measure the AC input voltage and Burden resistors are provided to connect external CT secondary input for current measurement
  • Regulators generate 3.3V and 5V (MCU and ADC board), ±2.5V and 3V (ADC analog supply)
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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.

TIDUB80B.PDF (3740 K)

Reference design overview and verified performance test data

TIDRJM0.ZIP (1380 K)

Detailed schematic diagram for design layout and components


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


Detailed overview of design layout for component placement

TIDRJM4.ZIP (9909 K)

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


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

TIDRJM3.ZIP (2825 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

Precision ADCs

ADS131E08S24-bit 64-kSPS 8-ch simultaneous delta-sigma ADC with fast start-up for monitoring and protection

Data sheet: PDF | HTML
Analog temperature sensors

LMT87±2°C 2.7V to 5.5V analog output temperature sensor with -13.6 mV/°C gain

Data sheet: PDF | HTML

LM2903Dual differential comparator

Data sheet: PDF | HTML
General-purpose op amps

LMV614Quad, 5.5-V, 1.5-MHz, RRIO operational amplifier

Data sheet: PDF | HTML
Isolated DC/DC converters & modules

LM50177.5-100V Wide Vin, 600mA Constant On-Time Synchronous Buck Regulator

Data sheet: PDF | HTML
Isolated DC/DC converters & modules

LM5160LM5160 wide input 65V, 2A synchronous buck/Fly-Buck™ converter

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

TPS723200-mA, negative, adjustable low-dropout voltage regulator with enable

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

TPS732250-mA, high-accuracy, ultra-low-dropout voltage regulator with reverse current protection & enable

Data sheet: PDF | HTML
MSP430 microcontrollers

MSP430FR596916 MHz MCU with 64KB FRAM, 2KB SRAM, AES, 12-bit ADC, comparator, DMA, UART/SPI/I2C, timer

Data sheet: PDF | HTML
Shunt voltage references

LM4041BAdjustable, precision micropower shunt voltage reference with 0.2% accuracy

Data sheet: PDF
Supervisor & reset ICs

LM8364Active-low voltage monitor with low quiescent current & 2.5% threshold accuracy

Data sheet: PDF

Technical documentation

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Type Title Date
* Design guide High Resolution, Startup Analog Front End for Air Circuit Breaker Design Guide (Rev. B) Sep. 09, 2016
Technical article What’s the big deal about circuit breakers? Aug. 01, 2017
Technical article Tripping Point: Simplifying circuit breaker design using delta-sigma ADCs Aug. 10, 2016

Related design resources

Reference designs

TIDA-00498 Signal Processing Subsystem and Current Input Based Self Power for Breaker Applications (ACB/MCCB)

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