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ONET8501T AC Characteristics

avraka
Intellectual 855 points
Other Parts Discussed in Thread: ONET8501T, ONET8551T

Dear Alex Davidson,
One of my customer which is a major optic module manufacturer asked to help technical meeting with her about the ac characteristics of ONET8501T in detail.
However I cannot find the detail of that such as Unstressed sensitivity, Deterministic jitter, Input reffered RMS noise and the others. Are there any information about that or symptom which describe what is the meaning of at least?

  • 0
    TI__Expert 8915 points

    Hello,

    For your education I have attached a file with information regarding optical receivers. The customer should be familiar with this.

    Can you tell us more about the application since another TIA may be more suitable.

    Regards,

    Alex.

    Optical Receivers.pdf
  • 0 in reply to Alex Davidson
    Intellectual 855 points

    Really great thanks Alex.

    Can I ask you some more questions about ONET8501T?

    1. What is the internal On Chip Supply Capacitor Value?

    ==> I calculated the on chip capacitance as 159.2pF by using the following description on the datasheet.Am I right?  "The on-chip  low pass filter for the photodiode is implemented using a filter resistor of 220Ω and a capacitor. The corresponding corner frequency is below 5MHz."

    2. For a general reflow profile, peak temperature range is 220 +/- 5 degree. If my custmer use 200 degree for 1 hour during reflow process, ONET8501T would be damaged. Right?

    3. Could you share the sensitivity table in both case of 1310nm and 1560nm wavelength?

    4. In the datasheet, RSSI internal bias output offset current is tipically 10uA. My customer want to know the other optic device having below 9uA RSSi.

    5. The case having a smaller RSSI value than the reference is sometimes. Why this happen? My customer said there is no issues on PAD.

     

    Alex.

    Main issues on my customer is about RSSI. If possible, please kindly share the material of RSSI for my study..

    I'll update the status after tomorrow meeting.

     

     

     

     

  • 0 in reply to avraka
    TI__Expert 8915 points

    Avraka,

    Can you please let me know who the customer is?

    1. That is correct for the capacitor on the FILTER pads. There is also about 150pF from pad 3 to ground (VCC_IN decoupling) and about 360pF from pad 2 to ground (VCC_OUT decoupling).

    2. I would not recommend putting the die through the refolw process. If this is a chip on PCB application, the TIA should be mounted to the PCB with a conductive epoxy after reflow.

    3. The difference in sensitivity due to the wavelength is dependend upon the photodiode, not the TIA. The parameter that affects this is the responsivity.

    4. If they want a TIA with lower RSSI offset current then then should use the ONET8551T. This has a typical offset of 0.9uA.

    5. I am assuming they are referring to the RSSI gain being 0.5A/A. There is no particular reson for this. To determine the average RSSI current, they just ned to multiply this value by 2.

    The RSSI output is just a scaled current mirror of the input current.

    Regards,

    Alex.

  • 0 in reply to Alex Davidson
    Intellectual 855 points

    Dear Alex.

    In the datasheet of ONET8501T, f(L,3dB) - Low Frequency -3dB bandwidth value is typically 30KHz.


    If  I assume ONET8501T AC characteristics as a kind of band pass filter, does Low Frequency -3dB Bandwidth mean the starting edge of high pass region?

  • 0 in reply to avraka
    TI__Expert 8915 points

    Avarka,

    You are correct. The 30kHz low frequency cutoff is the start of the high pass region.

    Regards,

    Alex.