100W Automotive Non-Isolated, Synchronous Buck Pre-Regulator Reference Design

July 18, 2019 by Paul Shepard

The TND6290/D reference design from ON Semiconductor demonstrates the operation and the performance of a 100W non−isolated synchronous buck automotive pre−regulator, based on the NCV881930 synchronous buck controller with four NVMFS5C460NL 40 V N−channel MOSFET.

The reference design shows a complete design for an automotive pre−regulator for a broad range of applications, and highlights the capabilities of the NCV881930 controller.

It is designed so the power supply designer can adopt the circuit directly into a typical system design, making only minimal component changes based on the system requirements.

The design is meant to be a complete solution, but it also provides access to key features of the NCV881930. These include integrated compensation, low IQ and continuous synchronous mode, wide input range, overcurrent protection, external synchronization, adaptive non−overlap drivers, integrated spread−spectrum, and under voltage lockout.

(click on image to enlarge)

Key Features

  • Complete Automotive Reference Design
  • Synchronous Buck Converter with an Input Voltage Range between 6.0- and 16.0-V, Handles Peaks Up to 40V
  • 410kHz Switching Frequency for Maximum Efficiency
  • NCV881930 Low Quiescent Current Automotive Synchronous Buck Converter and Four NVMFS5C460NL 40V N−channel MOSFET
  • Small Form Factor PCB with Four Layers

Impact of Output Capacitance Configuration on Performance

The datasheet of the NCV881930 gives detailed recommendations for the output filter configuration (inductance, shunt resistance, and output capacitance) dependent on the output voltage and current.

(click on table to enlarge)

The table above shows the measurement results for various output capacitor configurations and their corresponding performance regarding ripple, transient response and phase margin.

Different sets of high capacitance ceramic and polymer capacitors were used for the measurements.

  • 1x 100nF, 50V, 0603, X7R, always populated muRata GCJ188R71H104KA12D
  • 22F ceramic, 16V, 1210, X7R muRata GCM32ER71C226ME19L 18F @ 5.0V dc, 2mΩ ESR @ 410kHz
  • 120F polymer Nichicon PCJ0J121MCL1GS 24mΩ ESR @ 100kHz
  • 220F polymer Nichicon PCJ0J221MCL1GS 15mΩ ESR @ 100kHz