An ADC-direct energy-efficient temperature sensor with a novel multi-range BJT-based transducer design is presented. Thanks to the novel transducer design, the proposed NPN-based sensor does not require any analog-domain pre-ADC signal conditioning. Through bias current control, the sensing range can be adjusted for different applications. Our simulation results show a 2.67x improvement in ADC dynamic range utilization for the military (-55C to 125C) and 3.8x improvement for the medical (0C to 100C) temperature ranges, respectively. An Incremental Delta-Sigma-based readout circuitry for the proposed sensor has also been implemented and the circuit- and system-level simulation results are presented. The entire design draws 2.6uA from a 1.2V supply voltage to yield a resolution of 0.01C for a conversion time of 100ms, achieving a resolution FoM of 3.12pJC2.