port direction change to output causes current spike

lpcware — Wed, 15 Jun 2016 19:33:19 GMT

Content originally posted in LPCWare by mspahr on Fri Apr 11 12:20:46 MST 2014
Port direction change causes current spike.

LPC11U35FET48/501

When P0,22 direction is changed to output, there is a large current spike
on VCC. It sags my 3.3V VCC supply to 3V. It is less than 1uS in duration.
It then takes my 25mA power supply 100uS to fully recover.
The processor is normally running about 11mA so I am guessing it spikes to
greater than 25mA.
None of the other 11 GPIOs that are set to outputs do this.
P0,22 has a 5K resistor to ground and a small FET gate.
Before the direction change, the IOCON is set to 0x80 (set to GPIO, no pull-up).
The data register is set to 0.
I have scoped the P0,22 at the time of the direction change and it is always
low, before, during, and after the direction change.
I can subsequently set P0,22 high and low and it causes no current spike.
This has been seen on multiple boards so it is not just a bad chip.

Re: port direction change to output causes current spike

lpcware — Wed, 15 Jun 2016 19:33:19 GMT

Content originally posted in LPCWare by nxp_apps on Thu May 01 11:38:43 MST 2014
Hi,

Can you re-run the experiment with P0.22 disconnected from the 5K resistor and small FET gate?

Do you see this occurring on another port pin?

Thanks.

nxp_support

topic Re: port direction change to output causes current spike in LPC Microcontrollers

port direction change to output causes current spike

Re: port direction change to output causes current spike