What is the correct connection for VCAP1 and VCAP2?

[exlabs]

Hello,

VCAP1 and VCAP2 are external capacitors for the core's voltage regulator.

The data sheet for the STM32F479VI states that, "Stabilization for the main regulator is achieved by connecting an external capacitor CEXT to the VCAP1/VCAP2 pins."

I interpret this as a series connection, like this,

Table 19 gives some more information,

It mentions "the two 2.2uF Vcap capacitors...", are they bypass capacitors that need to connect to ground, one for each pin? I looked around online and found people using this scheme,

 

1. Which scheme is correct?
2. Should I adjust the total capacitance to be 2.2u for the second scheme i.e 2 x 4.7uF would be OK?
3. Using two capacitors (as above) would decouple RF and half the ESR, which are both useful.

Regards,

 

[Andrew Neil]

 

 

See also AN4488, Getting started with STM32F4xxxx MCU hardware development