A temperature sensor comprising two ring oscillators and a frequency counter for wireless systems is presented in this paper which includes the feature of resolution scaling. The sensing element is embedded into the architecture of the ring oscillators. The sensor IC is fabricated on 130 nm IHP SG13C technology and occupies an area of 0.02 mm 2 . Experimental results show a resolution of 0.009 K/LSB to 0.6 K/LSB according to a conversion rate of 140 Hz to 9 kHz within a temperature range of -25 °C to 125 °C. The total power consumption is 160 μW at 1.2 V supply voltage. The basic of operation, the design and evaluation of the chip are presented.