A 28.4 pj per conversion ISFET-based pH sensing design for low-energy applications

Ion-Sensitive Field-Effect Transistor (ISFET) is an emerging technology that has the potential to be used for pH sensing and other ion-based sensing applications. In conventional ISFET designs, pH sensors convert H⁺ concentration into analog voltage before digitizing to binary bits. This paper proposes a digital-based ISFET design that minimizes the use of analog front end and directly converts pH into 10-bit binary output using digital comparators and a counter. Our simulation results in standard 65nm CMOS technology proved that the design has a resolution of 0.0437 pH with energy performance of 28.4 pj/conversion.