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question of switch IC use photodiodes circuit

Sangkyu Kim
Intellectual 290 points
Other Parts Discussed in Thread: AFE4490, AFE4400, TS3DS10224

Hi. I want to use switch ic or mux to select photodiodes.

The ten photodiode are used.

Photodiodes is photovoltaic mode, TIA is AFE4400 or AFE4490.

switch  frequency is 1000Hz or 2000Hz.

Only one photodiode is selected and the others are not selected. 

The photodiode is ODD-5WB opto diode.

1) would you recommend me to adequate switch or mux?

2)  Is there any problem?

  • 0
    TI__Mastermind 45475 points

    Sangkyu,

    You have identified the configuration (10:1 mux) and bandwidth (>1GHz) requirements.  Unfortunately looking at the signal switch tool on TI.com doesn't show any high bandwidth switches with that configuration 1 to many configuration.  I think the closet solution would be using a couple of the TS3DS10224 which is a high bandwidth 1:4 mux. 

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    TI__Genius 12631 points

    TIDA-01222_OnePager.pptxHello Sangkyu,

     I am an applications engineer from the high-speed amplifier product team. Adam brought this query to my attention. I am currently working on a reference design concept to help customer alleviate such problems. The concept is called bootstrapping where I use a high-speed buffer amplifier and ac couple the signal at the inverting node into the gate of the switch. This should reduce the apparent capacitance of the switch. The design is still in concept phase. I should have results by some time in October, however this is something you can try on your board if you would like results earlier. Let me know if you have any amplifier related questions.

    -Samir