I designed MC33908 circuit according AN4766 to provide power to MPC5744p. When I debug the hardware, there is a strange phenomenon. When I first turn on the 12v switch power supply, then provide power the MC33908, MC33908 did not give its output. But when I truned off the switch power supply and power supply connector still connet to MC33908, then I turned on the power supply again. MC33908 can provide power to MCU and AUX devices. The system works fine. I tried many times, the phenomenon can repeatly appeared. I tested the circuit many times. There is no fault on circuit. Can someone tell me why MC33908 has such a phenomenon? What can I do to improve it?
PS: The debug pin is active.