An Improved Linearity Ring Oscillator-Based Current-to-Digital Converter

Many biosensors produce single-ended current outputs. Lab-on-chip applications demand parallel readout channels requiring low area current-to-digital converters. High HD2 has limited the current controlled ring oscillator’s (CCROs) adoption as a low area, single-ended converter. This work improves CCRO open loop linearity by 10 dB. A wide-bandwidth current buffer is also designed. A low area (0.0025 mm
²
), low power (
$357 ~\mu \mathrm {W}$
), single-ended, and 1 MHz bandwidth converter suitable for array readout is presented with the measured performance.