A temperature sensor includes an open-loop delay line comprising plural delay cells and a multiplexer configured to select a first number of the plural delay cells; a delay-locked loop comprising plural delay cells and a multiplexer configured to select a second number of the plural delay cells; a clock coupled to an input of the open-loop delay line and to an input of the delay-locked loop; a detector having a first input coupled to an output of the open-loop delay line and a second input coupled to an output of the delay-locked loop; and a finite state machine configured to detect a transition in the output of the phase detector.