I'm using the TPS53819a in an application with 3.3V in and .066V out at 20A. VDD is driven at 5V. The switching frequency is set to 525kHz. The problem I'm seeing is that the switching waveform does 2 consecutive pulses, each with a width of around 480ns, then waits for about 4us, and the cycle repeats. I would expect 1 pulse of around 480ns every 2-2.5us. The problem with this behavior is that the effective switching frequency is now closer to 250kHz and the output LC has difficulty filtering this so the output ripple is quite high. Enclosed are a PDF of the schematic and screen captures of the switching waveform and output ripple. These were taken on the EVM, which was modified to match our application schematic, using a separate supply for VDD and VIN.
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