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TPS54618C-Q1: Why the frequency in buck rarely up to 4MHz?

Imelda Zhang
Expert 3815 points
Part Number: TPS54618C-Q1
Other Parts Discussed in Thread: TPS54618

Why the frequency in buck rarely up to 4MHz?

        I have a few assumption. If the frequency is too high,

  1. there will be narrow gap for dead time. Synchronization buck need dead time between upper MOS and  lower MOS.
  2. the Rboot need to be reduced and the voltage in SW will overshoot, which leading to EMI problem.
  3. Cboot may have not enough time to be charged, making the upper mos inoperative.
  4. Qg which represents the total amount of charge required by the gate may cannot have enough time to build up. The rising edge may not be so fast.

As to why it was 4 MHz instead of other numbers, I have no conclusion.

  • +1
    TI__Genius 14990 points

    Hi Imelda,

    Basically, fix frequency buck converter has the  on time limitation which is increase with the duty cycle and load of the device. Device will manage the switching cycle to regulate the output voltage inside min ton time spec. Min ton time will decide the max switching frequency supported by device in duty cycle and max load conditions.

    TPS54618 device can support switching frequency up to 2 MHz not 4MHz.  Generally switching frequency define for device is based most of the application requirements.

    Are you looking for device for higher frequency? Can you share more detail on max freq. spec?

    Thanks, Tanvee

  • 0 in reply to Tanvee
    TI__Genius 14990 points

    Hi,

    There is no activity on this thread for long. I am closing thread. Please feel free to open new thread.

    Thanks, Tanvee