Hybrid incremental-ΣΔ-ADC for ambient light sensing applications

Incremental delta-sigma ADCs are well suited for ambient light sensing applications due to their multiplex capability. Conventional ambient light sensor circuits consists of a current-to-voltage converter followed by an ADC. The proposed hybrid delta-sigma architecture integrates the current-to-voltage converter into the modulator loop. Circuit non-idealities of the current-to-voltage converter are thereby suppressed by noise shaping which greatly enhances the achievable resolution. Photodiode biasing as well as leakage current correction is realized by the fully differential current-to-voltage converter. The achievable resolution can be adapted by varying the conversion length.