A 0.003-mm2, 0.35-V, 82-pJ/conversion ultra-low power CMOS all digital temperature sensor for on-die thermal management

In this paper, a 0.35 V, 82 pJ/conversion ring oscillator based ultra-low power CMOS all digital temperature sensor is presented for on-die thermal management. We utilize subthreshold circuit operation to reduce power and adopt an all-digital architecture, consisting of only standard digital gates. Additionally, a linearization technique is proposed to correct the nonlinear characteristics of subthreshold MOSFETs. A bulk-driven 1-bit gated digitally controlled oscillator is designed for the temperature sensing node. Also, a 1-bit time-to-digital converter is employed in order to double the fine effective resolution of the sensor. The proposed digital temperature sensor has been designed in a 90-nm regular V _T CMOS process. After a two-point calibration, the sensor has a maximum error of ?0.68 to +0.61 °C over the operating temperature range from 0 to 100 °C, while the effective resolution reaches 0.069 °C/LSB. Under a supply voltage of 0.35 V, the power dissipation is only 820 nW with the conversion rate of 10K samples/s at room temperature. Also, the sensor occupies a small area of 0.003 mm².