A 512×576 65-nm CMOS ISFET sensor for food safety screening with 123.8 mV/pH sensitivity and 0.01 pH resolution

Internet-of-things (IoTs) need a common CMOS technology platform to build multi-modal sensor on chip. This paper shows a CMOS-based ion-sensitive field effect transistor (ISFET) pH sensor for food safety screening. A low-power high-gain subthreshold trans-impedance amplifier is integrated with an integration capacitor to form a readout scheme by pH-to-time-to-voltage conversion (pH-TVC), which greatly improves sensitivity of a single ISFET pixel. Fabricated in standard CMOS 65-nm process with the smallest pixel pitch of 4.4 µm, a 123.8 mV/pH sensitivity is achieved compared to traditional source-follower readout with a 6.3 mV/pH sensitivity. E. coli experiment further shows its great potential to monitor hygiene condition for food safety with a 0.01 pH resolution.