Miniaturized thermistor based thermal sensor

A thermal sensor comprising:

• a first resistor and a first capacitor, said first resistor being a thermistor;
• a first current source coupled to said first resistor and said first capacitor that alternately charges said first resistor and said first capacitor each to a reference voltage, Vtherm, and wherein an output of said thermal sensor is a function of a resistance-capacitance (RC) time constant of said first resistor and said first capacitor;
• two non-overlapping phases, a thermal signal generation phase Φ1 and a counting phase Φ2, wherein in the thermal signal generation phase Φ1, said first current source charges said first resistor to reference voltage Vtherm and discharges said first capacitor to ground, while in the counting phase Φ2, said first current source charge said first capacitor to Vtherm;
• and
• wherein said first current source is coupled to a first clocked switch S1 clocked with a clock signal having the thermal signal generation phase Φ1, and to a second clocked switch S2 clocked with a clock signal having the counting phase Φ2, and to a positive input Vin+ of an amplifier A1, and wherein the first clocked switch S1 is coupled to said first resistor which is grounded and wherein said second clocked switch S2 is coupled to said first capacitor which is grounded, and wherein a third clocked switch S3 clocked with a clock signal having the thermal signal generation phase phase Φ1 is coupled in parallel to said first capacitor, and wherein a negative input Vin− of said amplifier A1 is coupled to a node n1, which is coupled to a second capacitor and to a fourth clocked switch S4, clocked with a clock signal having the thermal signal generation phase Φ1, and which is coupled to an output of said amplifier A1, which outputs to a counter.