# What is the use of the capacitors in this schematic?

I'm using an STM32L476RG microcontroller where the recommended schematic is as follows -

I was wondering what the purpose of C25 and C22 were, as SB38 and SB32 are shorted on my Nucleo development board. So, what is the purpose of these capacitors when they are shorted?

Since the picture is unclear, I have attached the link to the reference manual here. The schematic is on page 64 of the STM32L476RG reference manual.

Why have they used C25 and C22 when SB38 and SB33 are shorted in the schematic?

• What VCAP? I don't see any VCAP. In fact, I can't read any of the text at all, due to it having been shrunk to oblivion. -1 because that should have been obvious. Closing as unclear. – Olin Lathrop Sep 27 '18 at 11:36
• Are C25 and C22 present on your (physical) Nucleo development board? – Peter Mortensen Sep 27 '18 at 16:09
• Obviously if a part is shorted, there's no purpose for it on your board. It may still be populated because producing a single universal board is cheaper than several custom boards with only a couple of caps missing. – Dmitry Grigoryev Oct 1 '18 at 7:03
• They are not shorted in the schematics. They are optionally shorted, as presence of SB38 and SB33 clearly indicates. Why they populated C25 and C22? To save you the trouble of soldering them yourself if for some reason you need SB38 or SB33 opened. – Maple Oct 1 '18 at 19:48

Based on experience with other devices from the STM32 family I can tell the Vcap is a capacitor used to the internal voltage regulator. This is a mandatory part.

However, the STM32L476RG does not have Vcap pins. But the STM32 families are closely pin compatible. With only a few modifications.

I suspect your example board is suitable for more than only the STM32L476RG, and can also be used for part that do need Vcap. On you're part it's just Vdd/Vss, as for why the jumpers are shorted.

There is also a note on the schematic, mentioning VCAP for the F200 and F429:

F200/F429:VCAP1
F373:SD_VREF+
F373:PB14
F373:PB15
F373:PD8
F030R8/F373:PF6 & F200/F429:VCAP2