In circuits with negative I − T dependences, timing failures
will occur at high temperatures; however, in circuits with
positive I − T dependences, timing failures will occur at low
temperatures. Positive I − T dependences approach nominal
voltages as technology scales [3], [4]; the positive dependence
has been reported at ∼85% of nominal voltage in a 90-nm
technology [5]. Thus, adaptive systems that vary the supply
voltage to reduce energy consumption or improve reliability
[6], [7] may have operating voltages in both the negative and
positive I − T regions. Existing temperature sensors [8]–[15]