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ADP5051 Failure Issue

twenty
on Oct 18, 2015

 

Hi everyone,

I use ADP5051 in my prototype board and encounter 2 issues during the testing. My schematic almost followed the evaluation board and with only component value changed for different voltage generation.

1. By pulling up the sync/mode pin, the regulator should work in the mode set by the register 6, which is fixed PWM mode by default. However, the channel 1 output 3.4V instead of 1.1V by design. Only by pulling the sync/mode pin low, the 1.1V can be generated. Why did it behave like that? Does it need to be programmed first before power on to update the register when pulling the sync/mode pin up?

2. After 1.1 V is generated as described above, I used the power good output to enable the channel 2,3 and 4. Immediately the channel 2 failed and output 12V. Measured the pin SW2 and the PVin2, and found they are shorted. Tried 3 boards and all got channel 2 damaged immediately after power on. But the rest 3 channels can still output correct voltage. I measured channel 2 output pin. It is not shorted to ground. My question is how would this internal MOSFET get shorted? Usually the excessive voltage or current may kill the MOSFET. But the input voltage is +12V and there is no load connected to the output. What kind of circumstance can cause the internal high side MOSFET shoot through?

For all the test mentioned above the actual load are disconnected with the regulator. So there is no electrical load for regulator during the test. Will it be a problem?
I am ordering a few more ADP5051 chips and will replace the failed ones and test. Any advice would be much appreciated.

Thanks and regards,
Fei