Natural Input Current Limit Reference Design for Super-Cap Charge Circuits


Design files


This reference design uses natural-input current-limit characteristics of the flyback topology. During start-up, even though the initial output voltage of the super CAP is zero, the primary winding current is always limited by the peak-switch current limit of TPS61087. Considering the duty cycle during soft-start, the input current will be lower than the peak-switch current-limit value of TPS61087 by nature. Therefore, no extra components are needed.

The primary winding and secondary winding share the same ground, so the flyback inductor does not need reinforced insulation. Basic insulation is enough. This is a compact design for the super-CAP charge-up circuit application.

  • 2.5-V to 6-V input voltage range
  • Can effectively limit the input current below 3 A
  • Isolates the input side and the output side when shut down
  • Low cost and small solution size
Output voltage options PMP15044.1
Vin (Min) (V) 2.5
Vin (Max) (V) 6
Vout (Nom) (V) 13.5
Iout (Max) (A) .4
Output Power (W) 5.4
Isolated/Non-Isolated Non-Isolated
Input Type DC
Topology Flyback- Non Sync
Personal electronics
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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.

TIDT003.PDF (339 K)

Test results for the reference design, including efficiency graphs, test prerequisites and more


Detailed schematic diagram for design layout and components

TIDRW00.PDF (94 K)

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

TIDRW01.PDF (97 K)

Detailed overview of design layout for component placement

TIDRW03.ZIP (503 K)

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

TIDCEL3.ZIP (1156 K)

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

TIDRW02.PDF (490 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

AC/DC & DC/DC converters (integrated FET)

TPS6108718.5-V, 3.2-A, 650-kHz / 1.2-MHz step-up DC/DC converter

Data sheet: PDF | HTML

Technical documentation

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Type Title Date
* Test report PMP15044 Test Results Apr. 13, 2018

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