nRF51822 not reset

[wan]

We are develop one product, it is power by four AA battery. It works fine. but now I found a problem. when I power off and then power on again, sometime it can not be reset. I monitor the VCC voltage of chip, found when I power off, and the VCC voltage will drop down, when it drop down to about 0.4V and power it on again, the chip will can not be reset. how to resolve this problem?

[Jon (jono)]

Edited: 0.4v was on an IO-pin, not VCC.

We have reproduced this error, one io pin remains at approx 0.4v over night. On the morning when powering back up to 3v3 @ 4ms the chip does not boot.

Software ligths led and delays first thing -> not a sw issue.

Repeated powercycles chip does not reset! During these cycles there are some residual potential on VCC in the range 0.4..0.1V

Has happened at least 4 times and on different units. Chip rev: N51822QFACA11544GA.

[Jon (jono)]

Nordic: Any news on this one? We're still experiencing this problem once in a while, especially a backup capacitor keeping the RTC active may keep this issue active for a very long while.

[Kenneth]

If this is big problem you may consider adding an off-chip reset circuitry, for instance a 1Mohm between nRESET(SWDIO) and GND may act as a low cost off-chip reset circuit. Though this will add an increase in idle current consumption in active mode with ~VDD/1Mohm = ~2uA.

Best regards,
Kenneth