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TPS543C20: Fixed frequency modulation confusion

Thomas Mandal Nilsen
Prodigy 20 points
Part Number: TPS543C20


Tool/software:

Hi,

I read in the datasheet of TPS543C20 that it employs "Fixed-frequency modulation" and that it is a "true fixed frequency converter".

It is not clear to me what this means. Is the frequency fixed or does it modulate the frequency? It is crucial for my application that the frequency remains fixed at all times and that there is no sort of spread spectrum modulation.

  • +1
    TI__Guru 56985 points

     

    My apologies about any confusion.  The TPS543C20 employs a fixed frequency, trailing edge pulse-width modulation architecture.

    The switching frequency is not modulated, and the SW rising turn-on is controlled by an internally generated fixed frequency clock.

    For increased switching frequency accuracy and frequency control, external SYNC can be applied to the SYNC pin.

    When enabled, API (Advanced Pulse Injection) allows the converter to generate an additional pulse during the normal off-time between fixed frequency clock cycles in response to a load transient to reduce the output voltage drop caused by the sampling delay of the fixed frequency clock.  This can be disabled by the selection of the MODE resistor.