Other Parts Discussed in Thread: TPS56221
We added a resistor and FET 2N7002 N-CH 60V to the design to allow controlled startup and shutdown.
When the FET switch is enabled, the +5V supply does not start.
Checked part values, temperature and current and there seems to be no issue.
The unit is operated at 300Khz but there is a large ripple current 3AMPS at 70kHz that may be the reason.
Attached a Pico scope capture file of the power enable (red), 12V supply(blue), 5V output (Yellow)
There is not a large droop on the +12V line to indicate a large current.
The enable line looks very clean.
The +5V starts to ramp but stops. The supply will try to restart every 50mS
Is there another internal fault condition that can occur causing this issue?