A Compact Thermal Sensor with Duty-Cycle Modulation on 1200 µm2 in 7nm FinFET

In this paper a PNP-based thermal sensor is described, which features a most simple circuitry using the current-mode approach. A single feedback loop generates a CTAT current and compares it to a PTAT signal. The same loop performs also the active integration of the difference current, which eventually controls a duty-cycle modulator. The design is self-clocked with only 3 DEM phases, and the temperature can be extracted from of a single IO at a remote location. This results in an ultra-compact solution with minimum integration effort, as required for hotspot sensing within digital area. A prototype occupies only 1200 µm2 in 7nm FinFET and consumes 21µA from a 1.25V supply. From simulation, it achieves a raw accuracy of ± 4.7˚C (3σ), which improves to ± 1.4 ˚C after a 1-point trim.