https://open-source-silicon.dev logo
#general
Title
# general
t

Ted

12/15/2021, 7:27 PM
What's the proper channel for asking about design rules? There's some rules I expect that I can't find any reference to
l

Luis Henrique Rodovalho

12/15/2021, 7:33 PM
Try #efabless.
t

Ted

12/15/2021, 7:33 PM
For the sky130 pdk?
l

Luis Henrique Rodovalho

12/15/2021, 7:35 PM
Yep. I guess you already know about https://skywater-pdk.readthedocs.io/
t

Ted

12/15/2021, 7:35 PM
yup
n

Nguyen Dao

12/15/2021, 10:35 PM
t

Ted

12/16/2021, 1:39 AM
So, first of all, thanks. But I don't see it. The rules I'm looking for are "maximum distance of mosfet diffusion to welltap". I expect it to be on the order on 10 micro-meters (could be 5um, could be 50um), and it might vary by device type. Right now all my grepping and skimming has failed to find anything about it.
n

Nguyen Dao

12/16/2021, 10:40 AM
It’s <15um as I remember, I used 25um (tap-to-tap) in my designs
l

Luis Henrique Rodovalho

12/16/2021, 11:57 AM
Maybe the problem is that sometimes it can be described as a antenna rule, so it can't be found among the periphery rules.
A rule that wasn't checked in my designs is about surrounding transistors with welltaps or any kind of full guardring, while their gates are connected directly to a pad.
t

Ted

12/16/2021, 4:36 PM
It's not an antenna rule though, because it doesn't have anything to do with electrostatic discharge or the device being destroyed. It's to warn you that the bulk connection is not solid and the voltage may drift - so the simulation/models will not represent the actual operation of the device. It also warns you about latchup.