Sensing evoked compound action potential (ecap)

A method comprising:

• when stimulation generation circuitry does not provide the electrical stimulation, causing, by processing circuitry, storage of a first voltage at a first terminal of sensing circuitry at a first calibration capacitor and causing, by the processing circuitry, storage of a second voltage at a second terminal of the sensing circuitry at a second calibration capacitor;
• after causing the storage of the first voltage at the first calibration capacitor and causing the storage of the second voltage at the second calibration capacitor and when the stimulation generation circuitry provides the electrical stimulation, switching out, by the processing circuitry, a first calibration switch to prevent the first voltage stored at the first calibration capacitor from changing and switching out, by the processing circuitry, a second calibration switch to prevent the second voltage stored at the second calibration capacitor from changing;
• while the first calibration switch is switched out and the second calibration switch is switched out and when the stimulation generation circuitry does not provide the electrical stimulation, determining, by the processing circuitry, a sensing signal based on the first voltage at the first terminal offset by a first calibration voltage stored by the first capacitor and based on the second voltage at the second terminal offset by a second calibration voltage stored by the second capacitor;
• and
• causing, by the processing circuitry, the stimulation generation circuitry to deliver the therapy to the patient based on the sensing signal.

A medical device comprising:

• stimulation generation circuitry configured to provide electrical stimulation to the patient;
• sensing circuitry configured to sense a first voltage at a first terminal and to sense a second voltage at a second terminal;
• and
• processing circuitry electrically connected to the sensing circuitry and the stimulation generation circuitry, the processing circuitry being configured to:
• when the stimulation generation circuitry does not provide the electrical stimulation, cause storage of the first voltage at the first terminal at a first calibration capacitor and cause storage of the second voltage at the second terminal at a second calibration capacitor;
• after the first voltage is stored at the first calibration capacitor and the second voltage is stored at the second calibration capacitor and when the stimulation generation circuitry provides the electrical stimulation, switch out a first calibration switch to prevent the first voltage stored at the first calibration capacitor from changing and switch out a second calibration switch to prevent the second voltage stored at the second calibration capacitor from changing;
• while the first calibration switch is switched out and the second calibration switch is switched out and when the stimulation generation circuitry does not provide the electrical stimulation, determine, with the sensing circuitry, a sensing signal based on the first voltage at the first terminal offset by a first calibration voltage stored by the first capacitor and based on second voltage at the second terminal offset by a second calibration voltage stored by the second capacitor;
• and
• cause the stimulation generation circuitry to deliver the therapy to the patient based on the sensing signal.