2023-05-24 11:49 PM
There was a phenomenon that booting was not possible during the low temperature test.
The NRST external switch is equipped with a 100pF capacitor.
The datasheet recommends installing 100nF.
However, I don't think it will be a problem because the MIN value is more than 300ns.
If you install 100nF, it will boot normally.
Why can't I mount 100pF?
RC= 8K (40K (internal pull-up resistor) // 10K (external pull-up resistor)) * 100pF
Over 300ns.
2023-06-02 04:03 AM
100 pF will release NRST very fast, Probably some internal "TEMPORIZATION" timing is not meet.
2023-06-02 05:31 AM
The capacitor should also block superimposed interference and prevent unwanted resets. That's why there is a recommended capacitance of 100nF.