Analog to digital converter with current mode stage

An analog-to-digital converter (ADC), comprising:

• an input terminal configured to receive an analog input voltage;
• a sub-ADC configured to sample the received analog input voltage signal in response to a first phase clock signal and output a first digital signal representing the analog input voltage signal in response to a second phase clock signal;
• a transconductance amplifier configured to sample the received analog input voltage signal in response to the first phase clock signal and output a first current signal;
• a current mode digital to analog converter (DAC) configured to receive the first digital signal and output a second current signal representing the first digital signal, the current mode DAC having a plurality of current mode DAC unit cells;
• a residual amplifier configured to receive the first and second current signals and output an analog residual voltage signal based on a difference between the first and second current signals;
• a residue ADC configured to receive the analog residue voltage signal and output a second digital signal representing the analog residue voltage signal;
• and
• an alignment and error correction circuit configured to combine the first and second digital signals.

An analog-to-digital conversion (ADC) method, comprising:

• receiving an analog input voltage signal;
• sampling the received analog input voltage signal in response to a first phase clock signal by a sub-ADC stage;
• outputting a first digital signal in response to a second phase clock signal subsequent to the first phase clock signal by the sub-ADC stage;
• converting the analog input voltage to a first current signal by a current mode digital-to-analog converter (DAC) stage having a current mode DAC, wherein the current mode DAC stage is configured to sample the received analog input voltage signal in response to the first phase clock signal;
• converting the first digital value to a second current signal by the current mode DAC, wherein the current mode DAC is configured to output the second current signal in response to the second phase clock signal;
• determining a difference between the first and second current signals to determine a residue current signal by the current mode DAC stage;
• converting the residue current signal to an analog residue voltage signal by the current mode DAC stage;
• converting the analog residue voltage signal to a second digital signal;
• and
• combining the first and second digital signals into a digital output signal representing the analog input voltage signal.