This paper presents a high resolution time-based resistance-to-digital converter for amp-less high-precision sensor application. In order to solve the trade-off between resolution and bandwidth, a time-to-digital converter (TDC) is combined with a resistance-controlled-oscillator. The TDC is used to measure the fractional part of oscillation period, which realize a high resolution and conversion rate with moderate oscillation frequency. Proposed fractional period estimation technique reduce the required number of TDC and save power consumption. A prototype system was developed and 23 ppm resolution of resistance change at conversion rate of 5kSps was experimentally demonstrated.