title: A Low-Power Wide Dynamic-Range Current Readout Circuit for Ion-Sensitive FET Sensors.
abstract: This paper presents an amplifier-less and digital-intensive current-to-digital converter for ion-sensitive FET sensors. Capacitance on the input node is utilized as a residue accumulator, and a clocked comparator is followed for quantization. Without any continuous-time feedback circuit, the converter performs a first-order noise shaping of the quantization error. In order to minimize static power consumption, the proposed circuit employs a single-ended current-steering digital-to-analog converter which flows only the same current as the input. By adopting a switching noise averaging algorithm, our dynamic element matching not only mitigates mismatch of current sources in the current-steering DAC, but also makes the effect of dynamic switching noise become an input-independent constant. The implemented circuit in 0.35 μm CMOS converts the current input with a range of 2.8 μ A to 15 b digital output in about 4 ms, showing a DNL of +0.24/-0.25 LSB and an INL of + 1.98/-1.98 LSB while consuming 16.8 μW.
authors.forename: Hyunwoo
authors.initials: H
authors.lastname: Son
authors.forename: Hwasuk
authors.initials: H
authors.lastname: Cho
authors.forename: Jahyun
authors.initials: J
authors.lastname: Koo
authors.forename: Youngwoo
authors.initials: Y
authors.lastname: Ji
authors.forename: Byungsub
authors.initials: B
authors.lastname: Kim
authors.forename: Hong-June
authors.initials: HJ
authors.lastname: Park
authors.forename: Jae-Yoon
authors.initials: JY
authors.lastname: Sim
mesh_terms: D000465:Algorithms; D000669:Amplifiers, Electronic; D025802:Electric Capacitance; D004867:Equipment Design; D005246:Feedback; D007477:Ions / Q000032:analysis*; D012815:Signal Processing, Computer-Assisted; D014173:Transistors, Electronic
chemical_list: D007477:Ions