12W SEPIC Power Supply Reference Design for Industrial Applications
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Key Document


The TIDA-00781 is a 12W SEPIC power supply reference design for industrial applications. It takes 12V nominal input voltage, and generates a 12V @ 1A output with 92% peak efficiency. The SEPIC converter topology allows voltage step-up and step-down conversion. The design covers a wide input range of 2.5V to 20V with a minimum start-up input voltage of 3.5V. When using a noisy 12V supply, the design can operate uninterrupted while maintaining a regulated 12V output. The reference design features the LM3481 as the SEPIC controller and uses a single coupled inductor to achieve compact solution size. The component area of the SEPIC is about 39 x 26 mm (1.5 x 1 inch). The reference board is layout-optimized for improved EMI performance.

The design can also use the output voltage to operate, which means after the output voltage reaches 12V under normal operating conditions, the input voltage can be reduced to as low as 2.5V with the system still maintaining output voltage regulation within 5%. Note that at input voltage of 2.5V, the high input current causes the inductor to heat up to over 130°C so this is not a recommended operating condition.

  • Input: 2.5V to 20V (3.5V minimum start-up), IC capable up to 48V input
  • Outputs: 12V @ 1A
  • 12W total output power
  • Peak efficiency 92%
  • Switching frequency 500kHz
  • Output voltage ripple less than 50mV
  • Compact 4 layer board, 1oz outer, 0.5oz inner copper layers
  • Board Size: 76.2x54.8mm; solution size: 710.3 mm2

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Schematic/Block Diagram

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Design Files

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(Output Voltage 1)
Vin (Min) (V)2.5
Vin (Max) (V)20
Vout (Nom) (V)12
Iout (Max) (A)1
Output Power (W)12
Input TypeDC
TopologySepic- CCM

TI Devices (2)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
CSD18503Q5A  40-V, N channel NexFET™ power MOSFET, single SON 5 mm x 6 mm, 4.3 mOhm  MOSFETs  Sample & Buy Not Available
LM3481  2.97V to 48V High-Efficiency Controller for Boost, SEPIC and Flyback  Step-up (boost) regulators  Sample & Buy View Design Kits & Evaluation Modules

CAD/CAE symbols

Part # Package | Pins CAD File (.bxl) STEP Model (.stp)
CSD18503Q5A VSONP (DQJ)| 8 Download
LM3481 Download Download

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Technical documentation

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User guide (1)
Title Type Size (KB) Date
PDF 1148 19 Oct 2015
Design files (3)
Title Type Size (KB) Date
ZIP 318 19 Oct 2015
PDF 103 19 Oct 2015
PDF 261 19 Oct 2015

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