Tiny SEPIC reference design with 12-V/ 2.5-A output PMP30491 (ACTIVE)

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Key Document


This reference design is a 12-V pre regulator reference design for multiple automotive applications powering up to 36-W. The used SEPIC topology allows to step up and step down the input voltage, so cranking down to 5-V is supported; the controller LM5122 itself allows cranking down to 3-V at reduced power level.  Due to continuous currents at the input of any SEPIC topology the reflected ripple is low, means conducted emissions are reduced just by using smart topology. For even lower EMI the design is able to operate in forced PWM mode, for best light load efficiency a true diode emulation could be selected via jumper.  Synchronous rectification results in full load efficiency 93% + and fine thermal behavior - by using a generic dual inductor from stock.


  • High full load efficiency 93% + achieved by synchronous rectification
  • Full automotive input range from 5-V cranking to 36-V load dump
  • Cost effective design by just two drivers/two FETs compared to four switch buck boost topology
  • Low noise design - fine over all EMI behavior
  • Supports fixed PWM mode at Fsw 200 kHz or true diode emulation
  • Transient response < 2% for 50% load change

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Design Files

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(Output Voltage 1)
Vin (Min) (V)6
Vin (Max) (V)18
Vout (Nom) (V)12
Iout (Max) (A)2.5
Output Power (W)30
Input TypeDC
TopologySepic- Synchronous

TI Devices (1)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
LM5122  3-65V Wide Vin, Current Mode Synchronous Boost Controller with Multiphase Capability  Step-up (boost)  Sample & Buy View Design Kits & Evaluation Modules

CAD/CAE symbols

Part # Package | Pins CAD File (.bxl) STEP Model (.stp)
LM5122 Download Download
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Technical Documents

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User guides (1)
Title Type Size (KB) Date
PDF 958 07 Dec 2018
Design files (6)
Title Type Size (KB) Date
ZIP 31 07 Dec 2018
ZIP 483 07 Dec 2018
PDF 598 07 Dec 2018
PDF 109 07 Dec 2018
PDF 158 07 Dec 2018
PDF 109 07 Dec 2018

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