An apparatus for determining temperature comprising: a proportional to absolute temperature, PTAT, circuit configured to provide a PTAT voltage comprising a voltage proportional to absolute temperature; a sense-resistor; a bandgap voltage reference circuit, BGVR circuit configured to generate a voltage across the sense-resistor wherein a reference voltage is provided between a first terminal and a second terminal of the BGVR circuit, wherein the first terminal and the second terminal couple to the sense-resistor; a calibration circuit for calibrating the BGVR circuit, comprising: a memory configured to store a predetermined calibration value as a digital word comprising a plurality of bits for use in calibration of the bandgap voltage reference circuit; a trim circuit configured to receive a trim value based on the predetermined calibration value to control where one or both of the first terminal and the second terminal couple to the sense-resistor for said calibration and the provision of the reference voltage; a dynamic calibration module configured to receive the PTAT voltage and based on detection of a change in the PTAT voltage, generate the trim value by one of adding or subtracting a predetermined number of bits from the predetermined calibration value and provide the generated trim value to the trim circuit; wherein the apparatus comprises an output configured to provide a signal indicative of temperature based on the PTAT voltage and the reference voltage. a proportional to absolute temperature, PTAT, circuit configured to provide a PTAT voltage comprising a voltage proportional to absolute temperature; a sense-resistor; a bandgap voltage reference circuit, BGVR circuit configured to generate a voltage across the sense-resistor wherein a reference voltage is provided between a first terminal and a second terminal of the BGVR circuit, wherein the first terminal and the second terminal couple to the sense-resistor; a calibration circuit for calibrating the BGVR circuit, comprising: a memory configured to store a predetermined calibration value as a digital word comprising a plurality of bits for use in calibration of the bandgap voltage reference circuit; a trim circuit configured to receive a trim value based on the predetermined calibration value to control where one or both of the first terminal and the second terminal couple to the sense-resistor for said calibration and the provision of the reference voltage; a dynamic calibration module configured to receive the PTAT voltage and based on detection of a change in the PTAT voltage, generate the trim value by one of adding or subtracting a predetermined number of bits from the predetermined calibration value and provide the generated trim value to the trim circuit; a memory configured to store a predetermined calibration value as a digital word comprising a plurality of bits for use in calibration of the bandgap voltage reference circuit; a trim circuit configured to receive a trim value based on the predetermined calibration value to control where one or both of the first terminal and the second terminal couple to the sense-resistor for said calibration and the provision of the reference voltage; a dynamic calibration module configured to receive the PTAT voltage and based on detection of a change in the PTAT voltage, generate the trim value by one of adding or subtracting a predetermined number of bits from the predetermined calibration value and provide the generated trim value to the trim circuit; wherein the apparatus comprises an output configured to provide a signal indicative of temperature based on the PTAT voltage and the reference voltage.