Sort of a general question/warning. On the caravel/caravan framework, there are two 3.3V sources, vdda1 and vdda2. Circuits using these voltages should be using

sky130_fd_sc_hvl

, correct? All the other standard cell libraries only have 1.8v rated mosfets.

yes

@User: These sources can be run at 1.8V, so it depends on the intent of the designer. The normal setup, and the general intent, is to have all

vdda

supplies at 3.3V and

vccd

supplies at 1.8V. But all of the user domains are independent, and unconnected on the development board except through jumpers. I don't know how well the high voltage clamps work at 1.8V, but the I/O cells are rated for VCCIO down to 1.8V, so I suppose they must still provide sufficient ESD protection at 1.8V.

Thanks for the feedback. So I guess if you're using 3.3V, be sure to use

sky130fd_sc_hvl

, but if vdda1 and vdda2 are 1.8V, you're free to use any library.

Right. But unless the designer really needed three or four independent digital supplies, then they would presumably use

vccd1

and

vccd2

, so I would think that the use of 1.8V devices on any

vdda*

supply should be flagged with a warning. Obviously mixed high- and low-voltage libraries on the same supply would be flagged as an outright error.