Where can find the high speed IO cells?

High speed I/O seems to have been something in development that is mentioned in the documentation in a couple of places but is nowhere to be found in the files we got from SkyWater. The Caravel version for MPW-two will support bare pads which @Can Wang is working on---just one of the power pads with all circuitry and most metal removed from around and under the pad so that the capacitive loading will be minimal and allow a 5GHz bandwidth. But any high speed drivers need to be developed.

@Tim Edwards I believe you mentioned there is a netlist in the Open_PDK release. Does that mean the layout cell exists as well already?

I am modifying one of the power pads to a high speed pad. @Amro Tork

Hi @Can Wang

@Amro Tork: The goal is to take the existing cell

sky130_fd_io__top_power_hvc_wpadv2

, which without an overlay cell is just a straight-through connection from pad to core, with a high voltage (3.3-5V) ESD clamp (unconnected) in the same cell under the pad. Because the clamp is directly under the pad, it is limiting the bandwidth of the circuit. So the project will take that pad and remove the clamp circuit from it, and any additional metal under the pad or close to it that is limiting the bandwidth. The sky130_fd_io library actually has a cell called

sky130_fd_io__analog_pad

but it has only a verilog module and nothing else. So my suggestion was to make the modified pad layout the

analog_pad

layout and schematic.

@Tim Edwards Totally agree with suggestion. @Eslam Morsie from our side should be able to help here if you need anything. @Can Wang Could you please give him some guidance?

@Amro Tork I am working on several things and the high speed pad is currently not at the top my to-do list. So, if you are not in an emergent need of such a pad, I will eventually release the modified pad through Tim to one of the public repos. Otherwise, probably you should start to look at it first if you have an emergent need or any special requirements specific to your project. Discussions and feedbacks are always welcomed. Thanks!

@Can Wang No problem. I'm just offering our help either in that pad design or if you are working on something else and @Eslam Morsie our intern could help you with this work. That would be great. I assume you are working on something like a SERDES or something similar. If yes, I would think there would be a great opportunity to cooperate on a single design. @Eslam Morsie is taking one cell at the time. It would be nice to have him work with someone on something collaboratively.