PMP8878: Gate driver supply current requirement in PMP8878

Hi Aneesh,

Thanks for your interest in our design/part, my name is Mamadou Diallo, I am the AE supporting low-side drivers in the High Power Drivers group.

On one hand, the drive current (or average driver current) as you know is dependent on many factors including load, supply range, switching frequency, bias capacitors among others.
The average drive current to turn-on/off the mosfets can be estimated using Iavg = Fsw * Qg,total. The switching frequency is internally set on the UCC25230 at 380-kHz and the synchronous MOSFETs have 55nC of total gate charge each, given that there are 2 parallel FETs, Qg,total = 110nC. The average current required is therefore 380kHz * 110nC = 41.8mA which the 12VS(12V/0.2A) supply can sufficiently handle.

On the other hand, the 4A peak current delivered at the UCC27324 OUT pins is the current during a short and specific duration of the driver sourcing transition. That peak sourcing capability of the gate driver comes from the VDD to GND bypass caps (placed close to the chip) and again depends on the supply range , gate resistor and capacitors size: larger (>1uF larger means higher peak current) low-ESR ceramic cap sources large peak drive current and another smaller (100nF) parallel low-ESR ceramic cap helps to deliver efficiently the required peak current while filtering noise.

Please let us know if you have further questions or press the green button if this addressed your question.

Regards,

-Mamadou