Are the VSS and AVSS pins internally connected?

[Luis Ber]

Hello community,

I have a little doubt. Are all the GND pins internally connected inside the microcontroller? Is the analog reference (AVSS) internally connected with the digital one (VSS)? If it not, how is the isolation between them?

I don't know where I can do the union between the analog AGND plane and the digital GND plane and I was thinking if I can use the microcontroller to perform internally the connection.

Thank you in advance!

Luis

[Danish1 · Accepted solution]

One potential confusion: AVss is the negative rail for the analog parts, but it is not always the negative reference for e.g. ADC conversions. It might be for low-pin-count parts, but higher-pin-count parts have VRef- and VssA brought out separately.

I had a look at one data sheet, and the absolute-max ratings state that the voltage between any of the Vss, VssA and VRef- must not exceed 50 mV. So there might be an internal connection.

But I would not want to rely on internal connections to carry any current. I think you are better off making the connection externally. If you are worried about earth loops, why not place the junction between the AGND plane and digital-GND plane beneath the microcontroller.

Hope this helps,

Danish

[Luis Ber]

Thank you very much Danish.

Finally, I have placed the juntion between the two planes beneath the microcontroller.

Luis