20- to 40-VIN, 50-W Space-grade isolated flyback DC/DC over-current protection reference design


Design files


Spacecraft bus voltages vary from the well-established 28-V to more than the 100-V typically used in highpower commercial communications satellites, this reference design shows an example for a space-grade 50-W isolated intermediary bus converter, while implementing over-current protection (OCP) limit function. This design features INA901-SP radiation hardened current monitor, LM139AQML-SP quadcomparator, and UC1901-SP to create an isolated feedback flyback with current sensing and overcurrent flags – the UC1843A-SP current mode PWM controller is used to switch the low side MOSFET of the flyback converter and provide voltage and current to the output, the UC1901-SP senses the output voltage and completes the loop for the isolated feedback. The INA901-SP senses the input current which is provided to the LM139AQML-SP to create an overcurrent flag.

  • Isolated magnetic feedback using UC1901-SP
  • Current sensing using INA901-SP
  • Overcurrent comparison using LM139AQML-SP
  • Pulse-by-pulse current limiting
  • Double pulse suppression
  • Multiple feedback paths supported
Output voltage options TIDA-070002.1
Vin (Min) (V) 20
Vin (Max) (V) 40
Vout (Nom) (V) 5
Iout (Max) (A) 10
Output Power (W) 50
Isolated/Non-Isolated Isolated
Input Type DC
Topology Flyback- CCM
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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.

TIDUEM0B.PDF (16385 K)

Reference design overview and verified performance test data


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


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

TIDCF59.ZIP (930 K)

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

TIDRYD0.PDF (1389 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

AC/DC & DC/DC controllers (external FET)

UC1843A-SPRadiation-tolerant QMLV, enhanced 30-V input, 1-A 500-kHz PWM controller, 100% duty cycle

Data sheet: PDF | HTML
AC/DC & DC/DC controllers (external FET)

UC1843B-SPRadiation-hardened QMLV, 30-V input, 1-A single-output 500-kHz PWM controller, 100% duty cycle

Data sheet: PDF | HTML
AC/DC & DC/DC controllers (external FET)

UC1901-SPSpace-grade QMLV with isolated feedback generator

Data sheet: PDF
Analog current-sense amplifiers

INA901-SPRadiation hardened, -15-V to 65-V, split-stage current sense amplifier with in-line filter option

Data sheet: PDF | HTML

LM139AQML-SPLow Power Low Offset Voltage Quad Comparator

Data sheet: PDF

Technical documentation

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Type Title Date
* Design guide 20- to 40-VIN, 50-W Space-Grade Isolated-Flyback DC-DC Over Current Protection (Rev. B) Jul. 30, 2019

Related design resources

Reference designs

PMP8904 TPS50601SPEVM MINI POL Reference Design TIDA-070001 3- to 7-VIN, Space-grade point-of-load (POL) reference design with redundant eFuse inputs for OCP TIDA-070005 3- to 7-VIN, 24-A IOUT, 0.95-VOUT, Space-grade current sharing point-of-load (POL) reference design

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