the8thhabit
Newbie level 6
- Joined
- Aug 19, 2024
- Messages
- 12
- Helped
- 0
- Reputation
- 0
- Reaction score
- 0
- Trophy points
- 1
- Activity points
- 120
I am currently designing a SAR ADC in cadence that uses a 10bit 20MS/s with monotonic structure. My questions are as follows.
1. When setting the unitcap of the CDAC, is it correct to use MATLAB to figure out the proper unitcap value based on the SNDR I am aiming for?
2. If I set the unitcap value to 5fF, when I try to configure the CDAC using MIM cap, I am unable to implement 5fF because the MIM cap value of MIM cap is greater than 5fF. How should I proceed with the cadence simulation in this case?
3. If I change the MIM cap option to configure CDAC from 1p0f to 1p7f, the cap area will be smaller, which will increase the variation. In sar adc, the mismatch of CDAC has a big impact on the adc linearity, and I wonder if changing the MIM cap option to 1p7f will not affect the linearity.
4. The unit caps in CDAC are very small values in fF, and I was wondering if you draw these unit caps directly when laying out.
And what are some ways to implement it?
5. I was wondering what the standard is for choosing between MOM and MIM for the caps that make up a CDAC?
I'm designing a SAR ADC for the first time and I'm having a lot of trouble. If you could help me, it would be very helpful. Thank you.
The figure below shows the structure I designed.
1. When setting the unitcap of the CDAC, is it correct to use MATLAB to figure out the proper unitcap value based on the SNDR I am aiming for?
2. If I set the unitcap value to 5fF, when I try to configure the CDAC using MIM cap, I am unable to implement 5fF because the MIM cap value of MIM cap is greater than 5fF. How should I proceed with the cadence simulation in this case?
3. If I change the MIM cap option to configure CDAC from 1p0f to 1p7f, the cap area will be smaller, which will increase the variation. In sar adc, the mismatch of CDAC has a big impact on the adc linearity, and I wonder if changing the MIM cap option to 1p7f will not affect the linearity.
4. The unit caps in CDAC are very small values in fF, and I was wondering if you draw these unit caps directly when laying out.
And what are some ways to implement it?
5. I was wondering what the standard is for choosing between MOM and MIM for the caps that make up a CDAC?
I'm designing a SAR ADC for the first time and I'm having a lot of trouble. If you could help me, it would be very helpful. Thank you.
The figure below shows the structure I designed.
