Shuchi Nagaria [3:11 PM] Hello , We have been working on implementing an ESD protection circuit using FreePDK45. Initially, we used the diode available in the

analogLib

, but we encountered simulation errors due to the absence of associated diode model files. To resolve this, we attempted to replace the diodes with NMOS-connected loads, but this configuration did not function as intended. Could anyone provide insights or suggestions on how to proceed with this issue? Any guidance on suitable replacements or how to properly configure NMOS/PMOS transistors to mimic diode behavior in this context would be greatly appreciated. Thanks! (edited)

The last I was aware of ESD design efforts companies were moving to active shunt circuits rather than passive diode connected FETs. Try searching the literature for that.

Might be worth taking a look at the xschem schematic for the gpio cell used in caravel. https://github.com/d-m-bailey/sky130_fd_io. See what sort of ESD structure they are using. Are you creating your own ESD structures for research reasons or have you found the 2kV HMB protection of the above mentioned one is not good enough?