Noise Reduction via Chopper Stabilization of Fully Differential Temperature Sensors for Hardware Security Applications

The analysis and design of a chopper-stabilized fully-differential temperature sensor is presented for future on-chip power monitoring applications, particularly for the detection of malicious circuits. When temperature sensors are employed to sense the power dissipation of nearby circuits based on electrothermal coupling on the chip, the signal quality is limited by flicker noise because the slowly-varying temperature gradients imply that the information of interest is at low frequencies. The proposed two-stage transimpedance amplifier architecture has been designed with a chopping technique for flicker noise reduction by modulating the differential input currents from the bipolar junction transistors used as temperature sensors. Simulations of the prototype sensor circuit implemented in 130 nm CMOS technology show a low output-referred noise of 0.38 mVrms over a bandwidth from 1 to 370 Hz, while exhibiting a high temperature sensitivity of 2.09 V/ °C. A noise analysis was performed to derive equations that aid the design process with regards to trade-offs of parameters affecting noise performance, such as the chopping frequency and feedback resistance of the transimpedance amplifier.