HI All, I have one question regarding the caravan wrapper for the analog design. Are

vdda1, vdda2

are internally connected (shorted) or are they separate nets? And how does vddio gets the required voltage? How is it internally connected? Can anyone please help me with these questions? Thank you.

In sky130,

vdda1

,

vdda2

,

vddio

etc. are separate power domains and are supplied from the pcb independently. The default caravel board supplies 3.3V to

vddio

and doesn't supply power to

vdda1

or

vdda2

, just breaks them out to some pins. In gf180 it's all different and several of the power pins are shorted together.

@naina singhal at the chip level, they are separate pins. See https://caravel-harness.readthedocs.io/en/latest/pinout.html At the daughter board level, they also appear to be separated. See https://github.com/efabless/caravel_board/blob/main/docs/Caravel_Board_Specs%20_clean.pdf

Hi @htamas @Mitch Bailey Thank you so much for your reply. I don't see any internal user connection to pin vddio. It is not present in the empty caravan wrapper but it is present in final gds I got after tapeout. One more thing are vssa1 and vssa2 are not connected together as well?

vddio

is not connected to the user project area, it is used by the caravel harness itself (e.g. in the io cells for level shifting the digital pins)

@htamas Ok. Thank you so much for your answer. I am using vdda1 for a 5V supply instead of 3.3V and designing my own board. I am not using any digital pin connections. Will 5V supply mess up with vddio connections in any way which may affect my circuit?

If you supply 5V to each of

vdda

,

vdda1

and

vddio

, and use 5V tolerant devices, you should be fine.

@htamas there is not vddio pin in empty caravan wrapper in between vssa2 and vccd2. There in no terminal. It just appears in final layout I got after tapeout job.

One more thing are vssa1 and vssa2 are not connected together as well?

The pad frame shows

vssio

,

vssd

and

vssa

connected to the same pin, but

vssa1

,

vssa2

,

vssd1

,

vssd2

are connected to separate individual pins.

@Mitch Bailey Sorry but I do not understand what does that mean. I do not see any pin names vssio, vssd and vssa in the empty caravan wrapper. I just see vssa1, vssa2, vssd1, vssd2.

The pins

vdda

,

vssa

,

vccd

,

vssd

,

vddio

,

vssio

are used by the padframe itself. The pins

vdda1

,

vssa1

,

vdda2

,

vssa2

,

vccd1

,

vssd1

,

vccd2

,

vssd2

are passed to your project embedded within the padframe. All of these pins are available from the outside.

Ok. @htamas. Thank you so much for answer. How are vdda1 and vdda2 not shorted if they are coming from same vdda? I am just confused about padframe. I will look into its design.

They don't come from

vdda

. Each of

vdda

,

vdda1

and

vdda2

is separate.

Ok. Thank you. 🙂