==============================================================
Guild: wafer.space Community
Channel: Information / questions / Do we need OCD IO pads for digital 3v3 design
After: 2026-05-31 11:59 p.m.
Before: 2026-07-01 12:00 a.m.
==============================================================

[2026-06-08 6:38 a.m.] .pogeg
For our design, we're planning on using a pure 3v3 digital design (no analog, 3v3 SCL and SRAM). In that case, is switching from foundry provided IO pads to OCD pads necessary?


[2026-06-08 6:46 a.m.] mole99
No, it is not necessary. In this case, you can keep using the foundry pad cells.

The OCD cells add levelshifters between IO and core, which allows you to have IO voltage > core voltage. For example, you could have a 3.3V core voltage and a 5V IO voltage.

If you run everything at 3.3V, then you can simply use the FD cells.

Currently, there are no IO cells with 3.3V transistors (normal gate oxide). Both the FD and OCD cells use 5V transistors (thick gate oxide).


[2026-06-08 6:47 a.m.] mole99
As you probably know, the 3.3V SCL and SRAM are yet to be silicon verified.


[2026-06-08 7:28 a.m.] 246tnt
Also to note the foundry cells although designed for 5V provide more than acceptable performance running at 3.3V. ( > 100 MHz without issues ).

{Reactions}
👍

==============================================================
Exported 4 message(s)
==============================================================