Skip to main content
Associate III
July 27, 2024
Solved

SMARTAG1 Power management passives

  • July 27, 2024
  • 2 replies
  • 4112 views

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?

isaacseeto_2-1722080943900.png

 

isaacseeto_0-1722080859600.png

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

isaacseeto_1-1722080919299.png

 

This topic has been closed for replies.
Best answer by Peter BENSCH

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

2 replies

Peter BENSCH
Peter BENSCHBest answer
ST Technical Moderator
July 29, 2024

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.
Associate III
August 3, 2024

Ok thank you.