I’ve had a look through the data sheet at http://cache.nxp.com/documents/data_sheet/LPC178X_7X.pdf?pspll=1 and I can’t find out how fast the power rail has to come up.
I was thinking of using the following load switch,
It has a rise time of about 100us. Can someone tell me if the G120 will start clean with that slew rate.
I had this issue recently with a G120,where to meet the automotive EMC standards, the power supply has a slow rise time. With the reference design taken from the old Cobra 2, the resistor and capacitor on the reset line was too fast and the device would hang. A simple change to a 1uF cap and 100K resistor got the board working each time.
So just delay the reset long enough until the supply is stable and you should be OK with any supply. Or you could use a reset IC that does this for you and holds the reset line until the supply is stable. That for me was more expensive that the resistor and capacitor