Highly accurate temperature sensors, and calibrations thereof, for use with implantable medical devices

A temperature sensor for use in an implantable medical device (IMD), the temperature sensor comprising:

• a diode device;
• a plurality of current sources;
• a controller configured to control alternating between providing a first amount of current and a second amount of current produced using the current sources, or subsets thereof, to the diode device, to thereby alternate between producing a first base-to-emitter voltage drop (VBE1) and a second base-to-emitter voltage drop (VBE2) using the same diode device;
• and
• a sigma-delta modulator including a capacitor configured to alternate between storing the VBE1, which is complimentary to absolute temperature (CTAT), and storing a ΔVBE=VBE2−VBE1, which is proportion to absolute temperature (PTAT);
• the sigma-delta modulator configured to produce a signal having a duty cycle (dc) indicative of the ΔVBE:
• wherein the sigma-delta modulator includes a summing node, an integrator, a 1-bit quantizer, and a 1-bit digital-to-analog converter (DAC), the integrator including an operational amplifier (op-amp) having first and second inputs and an output, with one of the first and second inputs coupled to the summing node, and the integrator also including a switch between the output of the op-amp and an input of the 1-bit quantizer;
• wherein the same capacitor that is used to store both the VBE1 and the ΔVBE is part of both the integrator and the 1-bit DAC of the sigma-delta modulator;
• and
• wherein the switch is controlled to selectively couple the output of the op-amp to the input of the 1-bit quantizer.

A method for producing a temperature measurement for use in an implantable medical device (IMD), the method comprising:

• alternating between producing a first base-to-emitter voltage drop (VBE1) and a second base-to-emitter voltage drop (VBE2);
• alternating between using a capacitor to store the VBE1, which is complimentary to absolute temperature (CTAT), and using the same capacitor to store a ΔVBE=VBE2−VBE1, which is proportion to absolute temperature (PTAT);
• using a sigma-delta modulator that includes the capacitor to produce a signal having a duty cycle (dc) indicative of the ΔVBE stored using the capacitor;
• and
• producing a temperature measurement based on the signal having the duty cycle (dc) indicative of the ΔVBE;
• wherein the sigma-delta modulator includes a summing node, an integrator, a 1-bit quantizer, and a 1-bit digital-to-analog converter (DAC), the integrator including an operational amplifier (op-amp) having first and second inputs and an output, with one of the first and second inputs coupled to the summing node, and the integrator also including a switch between the output of the op-amp and an input of the 1-bit quantizer;
• wherein the same capacitor that is used to store both the VBE1 and the ΔVBE is part of both the integrator and the 1-bit DAC of the sigma-delta modulator;
• and
• wherein the method includes controlling the switch to selectively couple the output of the op-amp to the input of the 1-bit quantizer.