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LMZ31710: LMZ31710: Cin requirement

Yuxi Liu(Tony)
Expert 3200 points
Part Number: LMZ31710

Tool/software:

Hi TIer

I see there some requirement with Cin in datasheet 7.3.4.2.

I saw this non-ceramic capacitance was suggested to be added to improve the load adjustment rate, but my customer is using sensitive power supply equipment such as DDR, FPGA, etc.,

So can I recommend that the customer use ceramic capacitance paralleling instead of this non-ceramic capacitance. What are the risks? 

Why non-ceramic capacitance increases the load adjustment rate？

  • +1
    TI__Expert 5990 points

    Hi Yuxi Liu

    The non-ceramic capacitors on the input are for energy storage responding to the load transient.  The risk of using ceramic capacitors is the input capacitors resonating with source inductance from the supply powering the input.  Without the higher ESR of the non-ceramic input capacitors, there may not be sufficient damping to prevent input resonance.

    That risk can generally be addressed if there is a ferrite bead in series with the input, providing sufficient damping to mitigate input supply resonance.

    Thank you

    Savith