Proper powering of STM32` MCU on a custom PCB

[hashtala]

Hello guys

I am developing my own PCB where I want to use a STM32F767 MCU. I went ahead and figure out how to load binary and all but there is one thing that confuses me

so from the schematics (datasheet) my MCU has more than one VDD and VSS (ground)

I am guessing that these are for different peripherals of the MCU. If not please correct me. BUT if that'ss the case, how do I figure out which VDD to wire up in order to activate appropriate block of the MCU.

Do I actually need to wire up all of them correspondingly ? (with their capacitors and all)

Thanks!

[TDK]

> Do I actually need to wire up all of them correspondingly ? (with their capacitors and all)

Yes, with decoupling caps. All VDD/VSS/VCAP/VDDA/VSSA pins are mandatory. The reference manuals give the power requirements, but the nucleo/discovery board schematics are useful resources as well.

[hashtala]

OK got it.

But I do not understand why they have to make this that way

[RMcCa]

Probably because it's a big complicated chip. The datasheets strongly advise against trying to reduce the number and size of the the bypass caps, so they must be important.​

[TDK]

> But I do not understand why they have to make this that way

Ultimately, it comes down to cost. Nobody wants to pay an extra $0.10 per chip, so ST is going to make decisions that best position their chips in the market (e.g. lower the cost).

It's very common to have multiple VDD/VSS pins for bigger and more complicated ICs. This isn't just an ST thing.