Other Parts Discussed in Thread: AM5718, AM5718-HIREL
Hi,
We're using the TPS659162 to power a AMX5718 processor on a custom board. During the initial bring up of this design we've run into an issue whereby LDO1 comes up last in the sequence as one might expect, but then turns off after about 800us-900us. The LDO1 voltage then drops linearly to 0.8V. About 1ms later RESET_OUT asserts low and then this cycle repeats with LDO1 turning back on and off every ~8ms or so. This can be seen In the scope captures below where CH2 is the output of LDO1 and CH3 is RESET_OUT. Note:the second capture just has the horizontal axis zoomed in and the last capture increased the vertical axis to get a better measurement of the voltage out of the regulator.
We were speculating that perhaps the LDO's short circuit protection was tripping causing it to be disabled after the processor came out of reset. However there's nothing else that really loads this net beside the VDDSHV8 domain in our design, so this seems unlikely unless something is out of spec. We're considering modifying the board to make a current measurement to rule it out anyway. Any possible suggestions or explanations for why the voltage would turn off like this would be helpful.
Thanks,
John