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LP8764-Q1: Selection and Optimization of Buck Output Capacitors

zhang.li132
Prodigy 10 points
Part Number: LP8764-Q1

Under the application conditions of 3.3V input and 0.8V/20A output, the output capacitors of buck1-4 in TI reference design are all configured with 1210/47uF * 3. What is the reason for choosing such a large margin? Because if calculated based on a single 5A output current, it seems that a single 22uF can also meet the design requirements. In this case, can the capacitance of the output capacitor be optimized to 22uF * 4?

  • 0
    TI__Genius 12921 points

    Hello Zhang,

    the device expert is out, please expect a delay in the response accordingly.

    Best regards,

    Nicholas

  • 0
    TI__Expert 4501 points

    Hello,

    The output capacitance depends on the phase, switching frequency and voltage range on the output. What is your specific case ?

    Otherwise as you pointed out, in a 4.4MHz multi-phase configuration, a local output capacitance of 22uF per phase is enough as long as the total output capacitance including point-of-load is included between 50uF and 250uF per phase.

    Higher values are selected to take into consideration derating affecting capacitance.

    Best regards,

    Florian

  • 0 in reply to Florian Gabelle
    Prodigy 10 points

    First of all, thank you for your reply, by the way, we are now working on the TDA4_VL platform, and I still have some questions. in a 2.2MHz multi-phase configuration,in the SPEC of LP8764, it is mentioned that the range of buck Cout_total value is 100uF~1000uF. In the range of 100uF to 1000uF，What if we decrease the Local Cap_value from 47*2 to 22*1 per phase? Does this have any adverse effects? Our goal is to reduce costs by minimizing the number of capacitors required while satisfying performance.

  • +1 in reply to zhang.li132
    TI__Expert 4501 points

    Hello Zhang,

    The performance of the device is only guaranteed if the specifications from the datasheet are followed.

    In the case of a 2.2MHz multiphase configuration, the recommended local capacitance is 22uF and the total capacitance including point-of-load is between 100uF and 1000uF. If you have adequate capacitance at the point-of-load, this will be correct.

    Best regards,

    Florian