What is the flow to design a, let's suppose 2 bit Sigma delta modulator? Would Xschem be all i would need or is there a particular set of applications, since the design is mixed signal in nature.
02/22/2022, 10:17 AM
The design flow I'm using:
• Design circuit: Xschem + ngspice. Simulate until requirements are fulfilled using TT models.
• Verify for all process corners, voltages, device mismatch, temerpatures: Xschem, ngspice, home-made python scripts.
• Layout + LVS + DRC: Magic and netgen
• Post layout simulation: Again all process corners etc. (see above)
All in all it's a lot of work. I'm currently implementing a precision current source and a low noise / high bandwidth TIA and it takes monthes to get good results.
If you can I'd recommend to copy the design or parts of it (OTA) from previous caravels.
Btw. a Simga delta modulator is also on my to-do list. If all goes well I'll submit it for MPW-6. It will most likely be only 1 bit, ideally ~100MHz sampling.
02/22/2022, 12:11 PM
Thank you Simon for sharing your workflow with me, it will definitely help me a lot!
Also all the best to you, I hope you are able to complete your designs and send it off for tapeout.