This paper presents a multi-range ultra-lower power high accuracy CMOS smart temperature sensor based on substrate BJTs and a first-order incremental delta-sigma analog-to-digital converter (ΔΣ-ADC) targeting on applications where accuracy and power have higher priority over the sensing range and speed requirement. By using a reconfigurable pre-gain stage, the input range of the ΔΣ-ADC can be optimized for different application specific temperature sub-ranges, relaxing the resolution as well as power requirements for subsequent analog-to-digital conversion. High accuracy with reduced control circuit complexity is achieved through the use of dynamic element match (DEM) and multi-cycle integration. The proposed CMOS temperature sensor is designed for three temperature sub-ranges (-20°C to 7°C, 5°C to 35°C, and 33°C to 60°C) using a standard 0.18μm CMOS technology. An inaccuracy of ±0.1°C is achieved in all the three sub-ranges using only one-point calibration while consuming 1μW.