Request regarding the Power supply scheme of the STM32F303CC

[Luk937]

I currently try to design a custom PCB using the STM32F303CCT6TR, as I need a lot of IO ports and it fitted the job quite well.
I'm a computer science Student so please excuse my lack of in depth knowledge, but I haven't found a solution to the problem yet.
As I move components on the schematic I got confused about the Power supply scheme stated in the documentation.
(The picture)
The connection of VDD to the filtering capacitors, in particular.
As the drawing stated 4xVDD to VDD-Source and through 4x100nf + 4.7uf to ground. (with "uf" stands for micro farad)
There are multiple ways I interpreted it.
1. connect one 100nf to each VDD and further let them share a common 4.7uf capacitor.
2. connect each VDD to 4x100nf +4,7uf capacitors, so 5 capacitors per VDD (totaling in 20 capacitors).
3. connect each VDD to a 100nf and an 4,7uf capacitor. (as brackets could have be omitted)

Further, just to clarify the "+" refers to a parallel connection between the capacitors (it would make the most sense but then why didn't the specify it as 1010nf instead of 10nf +1uf ? (same applies for the above but I want to make the example simpler)

Best regards

[AScha.3 · Accepted solution]

>1. connect one 100nf to each VDD and further let them share a common 4.7uf capacitor.

Right.

+

 1010nf  is what ????

10nf +1uf  is 10nF and 1uF . ok ?

[SofLit]

Hello,

The easiest way to start to design an STM32 based HW is from the "getting started hardware" of the related microcntroller where you can get the details on how to develop a HW board around your MCU.

In your case, STM32F303, the related document is the AN4206 "Getting started with stm32f3 series hardware developement". In this AN we provide a HW reference design especially in the schematics section.

So to answer your question and based on the schematics I referred to, I share this part of the schematics on page 31:

100nF for each VDD and a common 4.7uF for all.

Hope it helps.

[Luk937]

Just a follow up question, For size constrains I plan to use the LQFP48 which has one VDD pin less, those this imply that only 3 100nF capacitors are used? or should the "additional" one should be placed next to the 4,7uF one? 

[SofLit]

The number of 100nF capacitors follows the number of VDD pins available on the package. So if there are 3xVDD on the package you need 3 x 100nF + 4.7uF