Electronic – the best way to connect two decoupling capacitors to an MCU

decoupling-capacitor

I was watching an STM32 PCB layout video by Phil’s Lab. At 1:55:19 he routes the traces between the STM32 MCU and the two decoupling capacitors. Here is a screenshot:

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He goes on and recommends to always connect decoupling capacitors like he did (from the MCU pin, into the two capacitors, and only then into 3V3), in order to maximize filtering.
My question now is whether this indeed is a better way to wire up decoupling capacitors when compared to this layout:

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I know that the closer the decoupling capacitors are to the MCU, the better. So in the end the answer might just be, that the routing solution that results in the shortest traces between MCU pin and decoupling capacitor is optimal?

Best Answer

First one agrees with Recommended PCB routing guidelines for STM32F4xxxx devices AN4488 Application note. Pin -> thick track -> cap -> via.

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Power supply decoupling All power supply and ground pins must be properly connected to the power supplies. These connections, including pads, tracks and vias should have as low impedance as possible. This is typically achieved with thick track widths and, preferably, the use of dedicated power supply planes in multilayer PCBs.

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