Wearable device having a micro-electromechanical system (MEMS) resonator for skin temperature sensing

A method for estimating skin temperature of a user wearing a wearable device having a housing and a micro-electromechanical system (MEMS) resonator, the method comprising:

• obtaining, at control circuitry of the wearable device, an output signal from the MEMS resonator, the output signal indicative of a temperature of a portion of the wearable device that contacts skin of a user when the wearable device is worn by the user and facilitates clocking of the wearable computing device, wherein the control circuitry comprises a phase-locked loop circuit comprising a demodulator, a local oscillator source, and a proportional integral derivative (PID) controller;
• demodulating, at the demodulator of the control circuitry, the output signal and a local oscillator signal generated by the local oscillator source of the control circuitry and indicative of a setpoint temperature for the portion of the wearable device;
• determining, at the control circuitry, a phase difference between a phase of the demodulated output signal and a phase of the demodulated local oscillator signal;
• determining, at the control circuitry, a temperature of the skin of the user has changed based, at least in part, on the phase difference being non-zero;
• in response to determining the phase difference being non-zero, adjusting, via the PID controller, the local oscillator signal to eliminate the phase difference;
• and
• providing, via the control circuitry, the output signal of the MEMS resonator to one or more computing devices of the wearable computing device to facilitate clocking of the one or more computing devices of the wearable device.