An 8nA-512μA Current-to-Digital Converter With Mixed-Signal Coarse-Fine Subrange Normalization

This brief presents a current to digital convertor (CDC) with low power, wide dynamic range and fast conversion speed. Proposed coarse converter extends the maximum input current range, and achieves fast conversion speed with the input adaptive control scheme. Capacitive transimpedance amplifier (CTIA) based fine converter digitizes the residue current and achieves fine resolution. Proposed mixed-signal coarse-fine subrange normalization technique enables seamless processing of the final converter output. The proposed CDC implemented in
$0.18 \mu \text{m}$
CMOS process converts input current up to
$512 \mu \text{A}$
with 7.8125nA resolution and
$400 \mu \text{s}$
conversion time. Power consumption is
$79.4 \mu \text{W}$
.