Design of Interface Circuits and Lightweight PUF for TMR Sensors

The micromagnetometers with high-resolution digital output are widely used in military and civilian fields. We proposed a novel high-precision interface circuit with an optimized chopper technique and switched-capacitor (SC) modulator for tunneling magnetoresistance (TMR) sensors. This work also proposes a novel method to create a lightweight physically unclonable function (PUF) by using existing TMR devices. The sigma-delta modulator converts the sensor signal into a robust digital output and maintains the signal-to-noise ratio (SNR) of the front-end circuit. We also take advantage of inherent variations of TMR sensors to generate PUF responses that are similarly unique and unclonable. The interface circuit is fabricated by a 0.35-
$\mu \text{m}$
CMOS process from the Shanghai Huahong foundry. The active area of ASIC is only about
$3\times2.7$
mm. The interface circuit can achieve an SFDR of 120 dB and an SNR of 98 dB at a sampling frequency of 200 kHz. The TMR magnetometers were tested in an environment of three-layer magnetic shielding. Our proposed PUF is also tested in terms of uniqueness and reliability.