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TPS54240-Q1 Synchronize to External Clock

Other Parts Discussed in Thread: TPS54240-Q1

Hi

My customer has questions about TPS54240-Q1.
Could you tell me about questions?

[Question]
 My customer want to change swithing frequency by external clock.
 ex. 400kHz -> 500kHz

1) Is there any specific about external clock range by RT resistor?
   ex. When RT=300k(=400kHz), how much can it input external clock range?

2) Is there any specific about duty of external clock?

Best Regards,

tateo

  • Hi tateo-san,

    With the way that synchronization frequency works in the TPS54240-Q1, there is no limitation between the RT set frequency and the synchronization frequency. The only thing to consider is that the LC output filter and compensation should be designed to support exepected range of switching frequencies.

    The duty cycle of the external clock is given by the 40 ns minimum pulse width specification in the electrical characteristics table.

    Best Regards,
    Anthony

  • Thank you for your support. My customer has one more question. When device synchronize to external clock, is there any specific about duty of switching frequency?

    Best Regards,

    tateo

  • Sorry for any inconvinience I may cause you. My customer want to know duty limitation in synchronizing to external clock mode.
    Could you tell me about duty limitation in synchronizing to external clock mode?

    Best Regards,

    tateo

  • Hi Tateo,

    Sorry for the delay, I was out of the office at the end of last week.

    When synchronizing to an external clock there is no added duty cycle limitation. The same as when using a resistor at the RT/CLK pin, the minimum duty cycle is limited by the minimum on-time.

    Best Regards,
    Anthony