Mixed chopping and correlated double sampling two-step analog-to-digital converter
A two-step, hybrid analog-to-digital converter (ADC) includes a Delta-Sigma ADC that employs chopping to resolve MSBs, a Nyquist ADC that employs correlated double sampling (CDS) to resolve LSBs, and a combiner that combines the MSBs and the LSBs to generate a digital output signal. The Delta-Sigma ADC has first and second integrators where, after resolving the MSBs, the first integrator is re-configured to function as a reference buffer for the Nyquist ADC and the second integrator is re-configured to function as the Nyquist ADC.
1. A two-step, hybrid analog-to-digital converter (ADC) for converting an analog input signal into a digital output signal, the hybrid ADC comprising:
a Delta-Sigma ADC that employs chopping to resolve one or more most-significant bits (MSBs) for the analog input signal;
a Nyquist ADC that employs correlated double sampling (CDS) to resolve one or more least-significant bits (LSBs) for the analog input signal; and
a combiner that combines the one or more MSBs and the one or more LSBs to generate the digital output signal.
2. The two-step hybrid ADC of claim 1 , wherein the Delta-Sigma ADC is a second-order Delta-Sigma ADC comprising a first integrator and a second integrator.
3. The two-step hybrid ADC of claim 2 , wherein the chopping is employed in the first integrator.
4. The two-step hybrid ADC of claim 2 , wherein the first integrator comprises CDS switches that are used to re-configure the first integrator to generate a reference voltage for the Nyquist ADC.
5. The two-step hybrid ADC of claim 2 , wherein the first integrator is re-configurable to function as a reference buffer for the Nyquist ADC.
6. The two-step hybrid ADC of claim 5 , wherein the second integrator is re-configurable to function as the Nyquist ADC.
7. The two-step hybrid ADC of claim 1 , wherein the ADC is implemented in a single integrated circuit.
8. A method for converting an analog input signal into a digital output signal, the method comprising:
performing Delta-Sigma ADC processing with chopping to resolve one or more MSBs for the analog input signal;
then performing Nyquist ADC processing using CDS to generate a reference voltage for the Nyquist ADC processing to resolve one or more LSBs for the analog input signal; and
combining the one or more MSBs and the one or more LSBs to generate the digital output signal.
9. The method of claim 8 , wherein the Delta-Sigma ADC processing is second-order Delta-Sigma ADC processing employing a first integrator and a second integrator.
10. The method of claim 9 , wherein the chopping is employed in the first integrator.
11. The method of claim 9 , wherein the first integrator comprises CDS switches that re-configure the first integrator to generate a reference voltage for the Nyquist ADC.
12. The method of claim 9 , wherein the first integrator is re-configured to function as a reference buffer for the Nyquist ADC.
13. The method of claim 12 , wherein the second integrator is re-configured to function as the Nyquist ADC.