davison7
Junior Member level 2
- Joined
- Aug 30, 2008
- Messages
- 22
- Helped
- 2
- Reputation
- 4
- Reaction score
- 1
- Trophy points
- 1,281
- Activity points
- 1,456
Currently, I have designed a second-order Sigma-delta ADC (fin = 20kHz, fs = 5MHz). In this ADC, a 2-bit flash ADC was adopted as a quantizer, and a 2-bit DAC was inserted into the feedback signal path. The attached file is the system architecture and the simulated results.
View attachment total.pdf
According to the output spectrum of the DAC, it does not show any noise shaping. This result makes me confused. Could anyone help me to check the circuit simulation is correct or not. Thank you very much!
In addition, I have some questions to be solved:
(1) How to simulate the ADC’s power spectral density (PSD)? In the aforementioned case, I choose the DAC output signal to do FFT, but the spectrum did not show the noise shaping.
(2) How to setup the transient simulation? The simulated stop time and time step should be set to what values so obtaining accurate results? Note that I choose the simulated stop time of 120 us and the time stop of 0.15 ns.
View attachment total.pdf
According to the output spectrum of the DAC, it does not show any noise shaping. This result makes me confused. Could anyone help me to check the circuit simulation is correct or not. Thank you very much!
In addition, I have some questions to be solved:
(1) How to simulate the ADC’s power spectral density (PSD)? In the aforementioned case, I choose the DAC output signal to do FFT, but the spectrum did not show the noise shaping.
(2) How to setup the transient simulation? The simulated stop time and time step should be set to what values so obtaining accurate results? Note that I choose the simulated stop time of 120 us and the time stop of 0.15 ns.
