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Formula of DCAP-2's Switching frequency

Satoshi
Guru 19485 points
Other Parts Discussed in Thread: TPS54325

Please let me know about formula of DCAP2's fsw.

【Background】

・TPS54325

・Vin：13V⇒Vout：5V/Io：0.62A

・Inductor：SPM6530T-3R3M

⇒On Webench report, fsw：583kHz

　　Customer want to know why fsw been low frequency (more than expected).

Best regards,

Satoshi

  • 0
    TI__Guru**** 191445 points

    There is no formula for the frequency.  TPS54325 uses DCAP2 control.  There is an adaptive on time controller and hysteretic off time comparator.  Together they set the nominal switching frequency.  There is no internal oscillator.  For Vout = 5 V and Vin = 13 V, characterization data suggests that you Fsw should be about 650 kHz.  I am not sure how webench calculates Fsw for TPS54325.