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MC33908NAE's strange phenomenon

Question asked by 心 赵 on May 12, 2018
Latest reply on May 16, 2018 by 心 赵


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.