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TPS40400: Dutymax question

Part Number: TPS40400
Other Parts Discussed in Thread: LMG1210

Hi Team

Would you advise my customer's question?

Duty max is defined for ex) as 85%(min) at Fsw=1.2MHz in datasheet.

Is this value change to higher value when Cload is less than 2.2nF described in datasheet below?

If there is a reference data which shows Cload vs Dmax, could you share it?

This is the question in case of TPS40400 's load is gate driver such like LMG1210 .

Thanks

Shidara

  • Hi,

    We are looking into this, will feedback to you soon.

    Thanks,

    Lishuang

  •  

    Yes, the maximum duty cycle of 85% at 1.2MHz is measured with the 2.2nF loads added to the gate drivers.  This loading increases the minimum OFF time by the high-side rise time but decreases it by the high-side Falling time.  Since the falling time is longer than the rising time, the net result is a slightly decrease in the minimum Off-time and increase in the maximum duty-cycle.

    Drivers with very low input capacitance and tightly matched propagation delays could result in closer matching of the rise and fall times, and a small increase in the minimum off-time coupled with a decrease in the maximum available duty-cycle.