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Layout Tips

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mscaff:
Hi,
I'm new to the forum and not sure if this is the right place to ask this, so, sorry if i'm at the wrong place.

I'm layouting a new PCB that has several power switched and linear power supplies a microcontroller and several ADCs.
After reading a lot, it seems that there is no unanimous answer for my questions so, I'll ask here and hope to get a better understanding about what should I do.

To be honest I think that it would be a great topic for a new video. :) :)

My question can be divided in 2 parts.

1) About the switched power supplies. Which is best?

a) To route for instance all the signals the shortest and widest in the top layer and connect with several vias to the plane in the inner layer just in 3 points (Vin, Vout and Ground). The idea here is to avoid spreading the noise and high currents from the PSW to the rest of the planes.

b) To use as much layers as possible in parallel. The idea here is to reduce the impedance as much as possible.

It seems to me that the 1st options is best, but I found a lot of conflicting information around.


2) In this board I have 4 x 24 bit ADC. How do I connect them?

a) Some say to just use a single solid ground plane and just place the Analog parts away from high speed and high current devices or in the path between them and the power supply. This is the easiest to me.

b) Some say to split the digital and analog planes and just connect them in a single place in the power supply. But since both of my supplies (3V3dig and 5Van) are created from the same input, they share the same ground from the beginning.

c) Most ADC datasheets say to split the digital and analog planes and just connect under the ADC. Again, my supplies (3V3dig and 5Van) are created from the same input so they share the same ground from the beginning AND should I connect the planes under All 4 ADC? Just under one of them?

Thanks, Mauricio Scaff

















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