On a STM32L4R9 one of our designs wants the VSSSDI pin to be connected to ground through a capacitor (not directly connected to ground) when the DSI is not used. But in the datasheet it states that if DSI is not used it should be grounded?

[DAndr.6]

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[Sarra.S]

Hello @DAndr.6​,

Your question is not really clear, what designs are we talking about ?

but the Ref man clearly states :

Hope that helps!

[DAndr.6]

Hi Sara,

Thanks for getting back to me. I am not allow to share to much but this is what is called and Active Electrical Cable (AEC) for QSFP. I see you pointed out that the VDDDSI pin but my email shows VSSSDI which should be VSSDSI. My mistake.

[DAndr.6]

So my question is what should be done with the VSSDSI pin when DSI is not used?

[Sarra.S]

Hello again @DAndr.6​,

As it is clearly stated in RM0432 paragraph 5.1.4, if DSI functionality is not used at all, then VSSDSI pin must be grounded