Does the STM32L4R9ZI package not include the VDD12DSI pin?

[solderballz]

I'm developing a schematic with the STM32L4R9ZIJ6 package (UFBGA144) for an embedded system that will use the DSI HOST API. However, this package doesn't seem to include the the VDD12DSI pin. What's this pin even for? and why is it on other packages like the LQFPs but not this one?

[TDK]

> Does the STM32L4R9ZI package not include the VDD12DSI pin?

It doesn't appear to have one in the datasheet. CubeMX agrees with the datasheet. However, it has a VCAPDSI pin which the datasheet says must be connected to VDD12DSI. I suspect it is either tied internally to VDD12DSI or the datasheet is incorrect. I may also be missing something. Maybe @Imen DAHMEN​ can take a look.

> What's this pin even for?

It's the for supplying 1.2V to the DSI, which is regulated internally and output on the VCAPDSI pin. Per the datasheet:

VCAPDSI pin is the output of DSI regulator (1.2 V) which must be connected externally to VDD12DSI.

VDD12DSI pin is used to supply the MIPI D-PHY, and to supply clock and data lanes pins. An external capacitor of 2.2 uF must be connected on the VDD12DSI pin.

[solderballz]

Thank you for your response, TDK. So based on this info -- the connection between the VDD12DSI and the VCAPDSI pin is necessary to make in order for the DSI HOST API to function. However, I haven't found any documented information that confirms that the VDD12DSI to VCAPDSI connection is made internally for this particular package.

Hopefully I will get an answer soon, because I've already ordered a couple of thousands of dollars worth of this part, and am working to spin this board ASAP.

[Imen.D · Accepted solution]

Hello @solderballz​ , @TDK​ ,

Sorry for the delayed reply on this.

I missed to come back to your post, when I have already taken action on your request.

I confirm that for the packages without VDD12DSI pin, the VCAPDSI is internally connect to VDD12DSI.

To avoid such confusion, this footnote will be added in the affected datasheets :

• VDD12DSI is tied internally to VCAPDSI (this is applicable for the packages without VDD12DSI pins).

Hope I answered your question :) .

When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

Imen

[Imen.D]

Please allow me to close this thread and marked the answer as Best, since it will help other users find that post faster.

Thank you again for having reported the point.

Imen