Calibration of continuous-time residue generation systems for analog-to-digital converters

A method to reduce mismatch of transfer functions of a forward path and a feedforward path of a continuous-time residue generation circuit, comprising:

• applying a test signal to a common input node of the forward path and the feedforward path;
• filtering a difference between outputs of the forward path and the feedforward path;
• digitizing the filtered difference to generate a digital output;
• measuring the mismatch of the transfer functions based on the digital output, which is generated as a result of the test signal being applied at the common input node;
• and
• adjusting one or more circuits in one or more of:
• the forward path and the feedforward path, to reduce the measured mismatch.

A continuous-time pipelined analog-to-digital converter, comprising:

• a continuous-time residue generation circuit having a forward path, a feedforward path, and a node to combine outputs from the forward path and the feedforward path, wherein the forward path and the feedforward path process a same input of the continuous-time residue generation circuit;
• test signal injection circuit to apply a test signal to the input of the continuous-time residue generation circuit;
• a quantizer to quantize a combined output of outputs from the forward path and the feedforward path;
• and
• a calibration circuit to observe a digital output of the quantizer generated as a result of the test signal being applied and to cause change in the forward path and/or the feedforward path in response to observing the digital output;
• wherein the digital output indicates whether the forward path and the feedforward path are mismatched.