A 20F 2 /Bit Current-Integration-Based Differential nand-Structured PUF for Stable and V / T Variation-Tolerant Low-Cost IoT Security
Jongmin Lee, Min-Sun Kim, Minhyeok Jeong, Gicheol Shin, Yoonmyung Lee · IEEE Journal of Solid-State Circuits · 2022
A current-integration-based differential NAND-structured physically unclonable function (PUF) with 20F2area per bit is proposed for low-cost IoT security. Current integration scheme with a capacitor is adopted to generate a response bit by comparing the delay of capacitor charging through pair of selected MOSFET transistors. For area-efficient implementation, minimum-sized MOSFETs are selected from NAND-flash-like array structure. By operating selected MOSFET pairs in moderate inversion mode, higher sensitivity to threshold voltage ($V_{\mathrm {th}}$) variation, and hence more stable response generation, is achieved while keeping it faster than weak inversion operation. A stabilization scheme based on current integration is proposed by discarding or remapping the transistor pairs that generate small charging delay difference. The proposed current-integration-based differential NAND-structured PUF (CI NAND-PUF) achieved high$V/T$variation tolerance of 0.145%/0.1 V and 0.120%/10 °C while limiting 20F2/bit area for 1-bit random response generation. With the proposed stabilization scheme, up to$11\times $and$7.7\times $BER improvement is achieved for trimming and remapping, respectively.