In an embodiment, a circuit includes: an error amplifier; a temperature sensor, wherein the temperature sensor is coupled to the error amplifier; a discrete time controller coupled to the error amplifier, wherein the discrete time controller comprises digital circuitry; a multiple bits quantizer coupled to the discrete time controller, wherein the multiple bits quantizer produces a digital code output; and a heating array coupled to the multiple bits quantizer, wherein the heating array is configured to generate heat based on the digital code output.