Fully on-chip temperature, process, and voltage sensors

A process, voltage, and temperature (PVT) sensor without a voltage/current analog-to-digital converter (ADC) or bandgap reference is proposed for high accuracy, low power, and wide voltage range portable applications. Conventional temperature sensors rely on voltage/current ADC for digital output code conversion. The proposed temperature sensor generates a clock frequency proportional to the measured temperature, and converts the frequency into a corresponding digital code. The generated digital code is still under the influence of PVT variations. Two distinct sensors for voltage and process monitoring are also proposed to enhance temperature sensor environmental variation immunity. The property of zero temperature coefficient (ZTC) bias point is used to remove temperature effect. The proposed wide voltage range low power PVT sensor is designed in UMC 65nm bulk CMOS technology. It is capable of operating over a wide voltage range within 0.3V~1V. The power consumption is no more than 3.7μW at 0.3V supply voltage and a high sample rate of 10k samples/sec. The temperature error is merely -0.8~0.8°C.