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TPS92515HV: How to decide SW frequency fsw?

Janson Lin
Intellectual 340 points
Part Number: TPS92515HV

I don't see any max/typ/min switch frequency information in datasheet. How to decide sw frequency? Is fsw depend on Vin , Vout or ILED?

Best regards

Janson

  • 0
    TI__Mastermind 25500 points

    Hello Janson,

    There is no minimum switching frequency for this device. The maximum switching frequency will be limited by the minimum on time (tLEB) and minimum off time (tD(off)). tLEB can be as high as 275ns and tD(off) can be as high as 120ns. So the period can be limited to a total of 395ns which limits you to about 2.5MHz.

    BUT, at that frequency and close to it the duty cycle cannot change by much so your input and output voltage range would have to be very limited. You also need to worry about the AC losses due to the switching frequency as described in the datasheet. So all in all I would say 1MHz or less is more practical.

    If you are looking to minimize the size of the circuit by increasing Fsw then you will need to go through the thermal calculations to see where your limit actually is. Keep in mind that this device is at its maximum Fsw at 50% duty cycle (or the closest point to it in any application). The Fsw depends on Vin, Vout, and inductor value. You can play around with the excel calculator if you like, it will give you a junction temperature estimate based on all of the thermals including AC losses due to Fsw.

    Regards,

    Clint