FMC_DAC_PSU PCB review: strong coupling between noisy P12V0 and clean analog supplies

sinara-hw / FMC_Shuttler

16-channel 125MS/s 16bit DAC in FMC form factor.

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FMC_DAC_PSU PCB review: strong coupling between noisy P12V0 and clean analog supplies #24

Closed mkiepiela closed 3 years ago

mkiepiela commented 3 years ago

There is strong capacitive coupling between P12V0 plane on P4 layer and clean analog supply polygons on adjacent P3 and BOTTOM layers (P3V3A, P5V0A and N3V0A). For assumed PCB stack-up and areas of polygons on P3 and BOTTOM the coupling to P12V0 reach the level of even dozens of pF.

Recommendation: split the P12V0 plane on P4 layer and connect to GND the areas under/upper supply polygons on P3/BOTTOM.

obraz

gkasprow commented 3 years ago

I moved the P12V0 to bottom layer. P4 is GND.