Calibration of integrated circuit time constants

An electronic circuit for calibrating a time constant comprising:

• a current source having a current output that is determined by a resistance and a voltage reference;
• a variable impedance coupled to said current source;
• a voltage storage element coupled to said current source for charging by said current source;
• a voltage comparator coupled to said voltage reference and to said voltage storage element for comparing a voltage of said voltage storage element to a voltage of said voltage reference;
• a counter coupled to said voltage comparator to measure the charge time required for said voltage of said voltage storage element to substantially equal said voltage of said voltage reference;
• and
• a circuit for adjusting said variable impedance until said charge time is substantially equal to a desired time constant, wherein said adjusting comprises successive approximation.

In an electronic circuit, a method of calibrating a time constant comprising:

• charging a voltage storage element of said electronic circuit;
• measuring a time required for a voltage of said voltage storage element to match a reference voltage as a charge time wherein said charge time is dependent on a impedance;
• and
• adjusting said impedance of said electronic circuit to make said charge time approximately equal a desired time constant, wherein said adjusting comprises successive approximation.