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ONET2591TA / response characteristics

Toshiyuki
Mastermind 7075 points


Hi,

Customer would like to confirm response characteristics of ONET2591TA.

We recieved a request for consideration.

Would you please provide us the information ? Kindly find the attached document for your review.

・optical input wave for APD

・APD characteristics

・APD conditions

amplification factor -> about 50

light sensitivity -> 500mA/W at M=1, λ=900nm

cutoff frequency -> 240MHz at M=50, λ=900nm, RL=50Ω 

capacitance between terminals of APD -> 8pF at M=50, f=1MHz

・PCB conditions

interconnection length from APD to ONET2591TA -> about 10mm

parasitic capacitance of layout -> about 1pF

If the power of optical input wave is -70dBm, -50dBm, -30dBm, -10dBm and +10dBm, please let me know what shape ONET2591TA could output ?

Best Regards,

Kato

  • 0
    TI__Expert 8915 points

    Hello Kato,

    Thank you for inquiring about the ONET2591TA.

    First, it should be brought to your attention that the ONET2591TA was not designed to be used with APDs. The cathode of the photodiode must be connected to the FILTER pad in order for the AGC to function correctly. The AGC circuitry monitors the voltage drop across the internal 220Ω filter resistor to set the AGC. Since an APD requires a high reverse bias voltage (typically greater than 10V) the cathode cannot be connected to the FILTER pad. Therefore, for some of your input conditions, the response will be distorted.

    Regarding the shape of the output pulse from the TIA, this is something that we cannot provide since this application is much different than what the part was designed for (Ethernet and Fibre Channel data communications) and the fact that the part is not recommended for use with APDs.

    Regards,

    Alex.