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TPS54240-Q1: Design Problem/Question with the Operating Frequency of the IC

Part Number: TPS54240-Q1
Other Parts Discussed in Thread: TPS54240,


I am designing a power supply using TPS54240-Q1 with 28 V nominal input voltage and 10 V output voltage. I used WEBENCH to design my circuit at first, however, solution size is larger than what I would like to have. Also WEBENCH does not let me choose the frequency of the device according to the datasheet. The IC can have a switching frequency as high as 2.5 MHz, and I would like to have my device operate around 1.5 MHz range for this operation. I have done calculations with respect to the selected switching frequency, but I am not sure since WEBENCH does not allow me to design the TPS54240 in such frequency. Below, I specify the requirements of the supply and would really appreciate if you can help me with the questions I have.

  • Input voltage = 18 - 32 V (absolute max.-min.), 28 V nominal
  • Output Voltage = 10 V 
  • Output current = 210 mA nominal, 500 mA maximum
  • Output Voltage Ripple = 1% of Vout

For 1.5 MHz operating frequency, output inductor value is calculated as 33 uH. Output capacitor value is calculated as 1.2 uF and it passes all the equations given in the datasheet. My questions are;

  • Can I trust the calculations made with respect to the datasheet and how realistic is my solution?
  • For input capacitance, which bypass capacitors should I be using to filter the input properly with respect to the given operating conditions?
  • Is there a way I can design the circuit on WEBENCH with the desired 1.5 MHz frequency?

Thank you.