Low-Power, Low-Noise Analog Front End Design for Circuit Breakers (ACB/MCCB-ETU)


Design files


This reference design is intended for use in molded case circuit breakers (MCCB) electronic trip units.  The op amp based design acts as current monitoring for over-current earth fault relays. Utilizing a low cost op amp, this design provides a pick-up (A) accuracy ±10 % and time delay (s) accuracy 0 to -20%. Additionally, this design takes harsh environment conditions in mind with features such as ambient insensitivity from  -10 to 70°C and high electromagnetic immunity. Finally the analog front end of this design seemlessly interfaces to TI MSP430 MCU for quicker evaluation and faster time-to-market.

  • Pick-up accuracy at ±10 % and time delay accuracy at 0 to -20% offer wide range of adjustment for maximum flexibility
  • Ambient insensitivity from -10 to +70°C for global design and worldwide acceptance
  • Excellent trip time repeatability
  • Wide input DC-DC converter with under voltage and overcurrent protection
  • Self-power (CT powered) supply with reduced CT loading and Power loss
  • Robust design that prevents phase reversal in overdrive conditions and high electrostatic discharge (ESD) protection (4-kV HBM)
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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.

TIDU224.PDF (1954 K)

Reference design overview and verified performance test data

TIDC291.ZIP (3361 K)

Detailed schematic diagram for design layout and components

TIDR415.PDF (426 K)

Detailed schematic diagram for design layout and components

TIDR416.PDF (204 K)

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

TIDC290.ZIP (287 K)

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

TIDU232.PDF (2328 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

Analog temperature sensors

LM62±2°C analog output temperature sensor, with 15.6mV/°C gain

Data sheet: PDF

LM293Dual differential comparator, industrial grade

Data sheet: PDF | HTML
General-purpose op amps

OPA4314Quad, 5.5-V, 3-MHz, low noise (4.6-nV/√Hz), 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

TPS550102.95V To 6V Input, 2W, Isolated DC/DC Converter with Integrated FETS

Data sheet: PDF | HTML
Isolated RS-485 transceivers

ISO117640-Mbps, half-duplex, isolated RS-485 & RS-422 transceiver

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

TPS71550mA 24V ultra-low-IQ low-dropout (LDO) voltage regulator

Data sheet: PDF | HTML
N-channel MOSFETs

CSD17571Q230-V, N channel NexFET™ power MOSFET, single SON 2 mm x 2 mm, 29 mOhm

Data sheet: PDF | HTML

Technical documentation

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Type Title Date
* Design guide High-Precision Analog Front-End Amplifier and Peripherals for MCCB Design Guide Feb. 25, 2014

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