Internal connection of Vdd and Vss

[cube sphere]

Posted on November 06, 2015 at 09:28

Hi,

STM32 uC have Vbat and several Vdd_n Vss_n pins.

Following the common guidelines each Vdd and Vss has to be connected.

However, I am wondering if there is a rule how these are internally connected. 

I suppose that all Vss are internally connected. But I am not sure, if all Vdd are connected internally. For example, I could imagine that each of Vdd supplies a module like peripherals or flash.

Any comments welcome. Thank you.

[Nesrine M_O]

Posted on November 06, 2015 at 15:03

Hi sphere,

I'd highly recommend you to have a look to the Power controller (PWR) section in your related product reference manual,it gives you an overview about Power supply scheme.

-Syrine-

[Tesla DeLorean]

Posted on November 06, 2015 at 17:18

The part runs internally at 1.25V, as I recall

The supply feeds a regulator, and localized pin drivers that drive the outputs at the interface voltages into external loads. Multiple supply pins allow for better current flow, more bonds to the die, reduces excessive current flows in the power rings, and placing decoupling closer to the drivers.

[cube sphere]

Posted on November 09, 2015 at 08:32

Hi,

many thanks to Syrine and clive1 for your fast response.

The mentioned overview I already had seen. But to be more specific I like to know what happens if one of Vdd is not connected properly. Does the controller continues to work and there might be some derating?

I have a controller with a sporadically undefined behaviour. As part of my investigation for the root cause I like to exclude the power supplies as a possible source of the problem. I suspect cold solder joints there. In the specific case, the outputs sporadically have undefined behaviour while all other subsystems continue to work.

Therefore, I was wondering if one of the Vdd exclusively supplies the I/O subsystem. If so this might cause the problems. If not, other Vdd should continue supply the I/O subsystem. Well, if this is an option, I have to check each supply in other ways.

Thank you.