Light to Frequency converter

[thavamaran]

light to frequency converter

Hi guys, i currently been working on this sensor TCS230, there is a portion of this sensor where is converts light to frequency, the datasheet is attached, so the
problem is i dont get the theory behind this conversion and through my
research i couldnt find any appropriate findings on this particular part, do
help me please.

 

[GSM Man]

It's a pretty simple circuit that's been in use using discrete parts for decades.

The ouput of the Photodiode ia a current that is proportional to the intensity of the light falling on it (within in its bandwidth). Its output drives a oscillator (basically a VCO, or ICO) whose frequency is proportional to the light level (more light = higher frequency).