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STM32L151 nRST pin... doesn't reset!

Question asked by olivotto.andrea on Apr 13, 2015
Latest reply on Apr 14, 2015 by olivotto.andrea
We are experiencing a very annoying issue... we have a portable application, STM32L151, DVdd=3.0 regulated via an LDO, lithium battery.

Randomly, the MCU freeze and the nRST does... nothing! We need a full power cycle to restart the application.

- We checked the Power supply and the layout, everything seems designed as it should be (100nF everywhere, 6 layer board).
- During freeze the power consumption is very low, and the pins seem floating.
- Freeze is not related to battery SOC.
- Only pins accessible are USB D+ and D-, with proper varistors protection.
- We perform ESD and burst tests, no freeze here.
- HSE external clock, 16MHz, works ok.
- Bootloader + application, both jump from active state to low power state (stop mode)
- Wake-up from stop mode using EXTI

Any hint?

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