Testing Circuit of a Longtime-Constant Circuit Stage and Corresponding Testing Method

A test circuit comprising:

• a charge-retention circuit for measurement of a time interval, the charge-retention circuit comprising a storage capacitor connected between a first biasing terminal and a floating node, and a discharge element connected between the floating node and a reference terminal, the discharge element configured to implement discharge of a charge stored in the storage capacitor by leakage through a corresponding dielectric,
• a biasing stage, configured to bias the floating node at a reading voltage;
• a detection stage configured to detect a biasing value of the reading voltage;
• and
• an integrator stage, including a test capacitor coupled to the floating node, configured to implement an operation of integration of a discharge current in the discharge element with the reading voltage kept constant at the biasing value, and to determine an effective resistance value of the discharge element as a function of the operation of integration, wherein the integrator stage further comprises an operational amplifier, having a first input terminal connected to the floating node and configured to receive the reading voltage, a second input terminal configured to receive a comparison reference voltage, the value of which is kept constant at the biasing value during the operation of integration, and an output terminal on which it is configured to supply an output voltage, wherein the test capacitor is selectively connected between the first input terminal and the output terminal during the operation of integration.

A method for testing a charge-retention circuit for measurement of a time interval having a storage capacitor coupled between a first biasing terminal and a floating node, and a discharge element coupled between the floating node and a reference terminal, the discharge element configured to implement discharge of a charge stored in the storage capacitor by leakage through a corresponding dielectric, the method comprising:

• biasing the floating node at a reading voltage;
• detecting a biasing value of the reading voltage;
• implementing an operation of integration of the discharge current in the discharge element with the reading voltage kept constant at the biasing value;
• and
• determining an effective resistance value of the discharge element as a function of the operation of integration.