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IVC102: Pico-ampere photocurrent front-end with switched integrator

Daniele Paesani
Prodigy 90 points
Part Number: IVC102
Other Parts Discussed in Thread: DDC112

Hello, 

I am in the process of designing a sensitive photosensor system, capable of measuring low photocurrents: as a reference, the dark current of the photosensor will be in the order of 10-100 pA. The light output to be measured is a steady, low intensity light source above the dark current.

For this application I was thinking about the following architecture, based on a switched integrator as TIA stage, as shown in the sketch below. Two comparators + timers will provide data conversion.

-Any comments or suggestions about the proposed solution?

-The IVC102 seems a good candidate for the application, or am I missing something? Any leakage issues to foresee?

-Other components or architectures to suggest?

Thank you!

DP

  • 0
    TI__Mastermind 49926 points

    Hello Daniele,

    This is a very old device and the system engineer who is familiar with the device will get back to you by next week.  

  • 0 in reply to Praveen Aroul
    Prodigy 90 points

    Thank you. I am aware the IVC102 is an old component. If the proposed architecture is valid, even different part numbers you can suggest, or a discrete op-amp + analog switch might be used in the design. 

    Thank you,

    DP

  • 0 in reply to Daniele Paesani
    TI__Expert 4680 points

    Hello,

    First of all, sorry for the delay. Being on business travel 3 of the last 4 weeks... Honestly, with the little I know about the IVC102 (as you said, that's an old component that I've never personally used), what you draw above should work. It looks like a smart approach to avoid the use of an explicit ADC but I have not implemented myself either such thing so don't know where the gotchas can be. Maybe watch with charge injection of reset switch but if I recall right, it was pretty good. Trying it out seems to be the only way to know for sure. 

    If you wanted to go with a straightforward approach, the DDC112 is the lowest channel count we got (2 channel) with ADC integrated, but again, don't see why I wouldn't use the above if you have experience with such scheme.

    Sorry can't be of more help,

    Eduardo