Poly Resistor Primitive Not Present ?

[shubham-analog]

Resistors would be required at numerous places in the design. A diode connected transistor or transistor as a resistor cannot replace resistor at all places.
As of now src/glayout/primitives/resistor.py contains a diode connected pfet as a resistor.

With reference to Chipathon 2025, gf180mcuD pdk provides some resistors. For the poly resistor there are 2 variant salicided(low sheet resistance) and unsalicided(high sheet resistance). If these two variants can be enabled as primitives, it would be really helpful.

[shubham-analog]

I did a quick check to see if all the layers required for poly resistors are present in src/glayout/pdk/gf180_mapped/gf180_mapped.py.
For npoly resistor,

Salicided	Unsalicided	Is Layer Avl. in Glayout
COMP2 22/0	COMP2 22/0	YES
POLY2 30/0	POLY2 30/0	YES
NPLUS 32/0	NPLUS 32/0	YES
PPLUS 31/0	PPLUS 31/0	YES
CONTACT 33/0	CONTACT 33/0	YES
METAL1 34/0	METAL1 34/0	YES
RES_MK 110/5	RES_MK 110/5	NO
-	SAB 49/0	NO

RES_MK 110/5 and SAB 49/0 are not present. I am assuming that the drc rules would also be not present for them.

[shubham-analog]

@msaligane @amisapta15 If these could be enabled, it would be helpful.

[amisapta15]

Sure. A similar thing has been done on Sky130 last year in a notebook submitted to VLSI, see Resistive DAC Generation section here

Please feel free to open a PR for the same in gf180. Contributions are very welcome.

[msaligane]

@shubham-analog @Subhampal9 @amisapta15 is any of you working on this? if not can we assign it to one of the new students?

[amisapta15]

Yes. Assigning this issue to someone would be very useful. It is an important element to add

[msaligane]

@ErinXU2004 can you please take a look?

[amisapta15]

Being tackled in #47 , Feedback welcome. Currently not DRC Clean.

[amisapta15]

Now being handled with #61