SMARTAG1 Power management passives

isaacseeto · ‎2024-07-27

Hi, I have been reading the "STM32L031x4 STM32L031x6" datasheet (attached) and referring to the SMARTAG1 schematic (also attached). Why does the MCU require 1 x 100 nF and 3 x 1 uF capacitors?

According to the power supply scheme, shouldn't there be 3 x 100 nF since there are 3 x VDD?

Peter BENSCH · ‎2024-07-29

The three 100nF + 1x1µF = 1.3µF buffer capacitors mentioned in the STM32L031 data sheet are the minimum configuration. The SMARTAG1 also contains four capacitors with a total capacitance of 3x1µF + 100nF = 3.1µF, which is significantly more than recommended. If you wish, you can also use smaller capacitors, but they should not have significantly more capacitance, as the STLQ015 may drive a maximum of 10µF.

However, it is more important that ceramic capacitors are used, which is the case in the SMARTAG1.

Does it answer your question?

Regards
/Peter

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Peter BENSCH · ‎2024-07-29

The three 100nF + 1x1µF = 1.3µF buffer capacitors mentioned in the STM32L031 data sheet are the minimum configuration. The SMARTAG1 also contains four capacitors with a total capacitance of 3x1µF + 100nF = 3.1µF, which is significantly more than recommended. If you wish, you can also use smaller capacitors, but they should not have significantly more capacitance, as the STLQ015 may drive a maximum of 10µF.

However, it is more important that ceramic capacitors are used, which is the case in the SMARTAG1.

Does it answer your question?

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

isaacseeto · ‎2024-08-03

Ok thank you.