Code-Division Multiplex Encoding Analog Front End for Current-Mode Sensor Arrays

This letter presents a new approach for applying orthogonal code-division multiplex encoding to current-mode sensor arrays with analog-domain encoding directly in the column readout circuitry, which enables simultaneous readout for multiple sensors. The approach is applied to a 8 × 16 array of CMOS-integrated photodetectors and implemented in a general purpose 180-nm CMOS process. The sensor array demonstrates 63-dB signal-to-noise ratio with an array-wide sampling rate of 100 Hz with 16-channel encoding, an improvement of more than 12 dB compared with time-division multiplexing at the same sampling rate. The complete photodetector array consumes 5 mW total power. This letter represents the first reported code-division multiplexed sensing architecture with analog-encoding front end, and the orthogonal coding scheme is broadly applicable to electronic current-mode sensor arrays for physical, chemical, and biological sensing applications without requiring sensor input encoding.