ISSCC 2018 / SESSION 19 / SENSORS AND INTERFACES / 19 . 5 19 . 5 A Current - Measurement Front - End with 160 dB Dynamic Range and 7 ppm INL

Accurate current measurement is crucial in many biosensing applications, such as the detection of neurotransmitters [1] and the monitoring of intercellular molecular dynamics. This need has become even more critical recently with single-molecule biosensors where sub-pA signal currents are superimposed on a slowly varying nA-to-μA background current, as is the case with nanopores [2]. As such, the readout circuitry requires wide dynamic range (>120dB) and high linearity (>14b) albeit often with low bandwidth (a few Hz to kHz). This paper presents a current measurement front-end using a modified asynchronous ΔΣ modulator architecture that achieves 7ppm INL and 160dB dynamic range (100fA to 10μA) for a state-of-the-art 197dB FoM due to: 1) a continuous-time, oscillatorbased Hourglass ADC that asynchronously folds the input signal within the supply, 2) noise shaping to suppress the quantization noise, and 3) a digital linearity correction technique that relaxes the amplifier bandwidth requirement thus reducing power.