Choosing Appropriate Capacitance Value on the C Pin for FM0+ Series MCUs – KBA222290

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Question:

How to choose an appropriate capacitance value on the C pin for FM0+ series MCUs to reduce power consumption?

 

Answer:

For FM0+ series device, instantaneous peak current value is largely related to the capacitance value applied on the C pin, when the device is woken up from DeepStandby mode.

 

The capacitance on the C pin gets charged and discharged whenever the device enters to and returns from the DeepStandby mode. This means that smaller capacitance values may cause a smaller current. However, the minimum value of the capacitance is 1 µF, and normal operation of the device cannot be guaranteed if the value is less than 1 µF. Meanwhile, the capacitance value has temperature dependency; it drifts with change in ambient temperature. Therefore, you should ensure that the capacitance value is always higher than 1 µF, while taking temperature drifts into consideration.