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ONET8501T connection to two terminals PD

INg
Genius 3475 points
Other Parts Discussed in Thread: ONET8501T, ONET8541T, ONET8531T, ONET8551T

Hi

My customer is working on ONET8501T. He is connecting a two terminal PD. Can i get some advise on which is the best way to connect up?

Ivan

  • 0
    TI__Expert 8915 points
    Hello Ivan,

    The ONET8501T is a high gain TIA and there is a high chance for an oscillation to occur if a two terminal PD is used, especially with TO-can packaging. It is recommended to only use a 3 terminal GSG type PD with the ONET8501T as shown in Figure 17 of the datasheet.

    If they only have a two terminal PD then a lower transimpedance TIA such as the ONET8531T or ONET8541T should be used and a layout example is shown in Figure 17 of the ONET8541T datasheet.

    Alternatively, if it is desired to use a high gain TIA then the ONET8551T can be used. The ONET8551T has a unique design compared to the ONET8501T that allows high gain without an oscillation occurring when used in a TO-can. An example layout is shown in Figure 7 of the ONET8551T datasheet. It is my recommendation to use the ONET8551T.

    Regards,
    Alex.
  • 0 in reply to Alex Davidson
    Genius 3475 points

    HI Alex

    Thanks for your feedback. My customer is reviewing the feasibility of 8551T.

    Like to run by you again, in the event that 8051T has to be used, would below be the best way to lower the chance of oscillation?

    Of course, all wire would need to be same length and as short as possible, is that correct?

  • 0 in reply to INg
    TI__Expert 8915 points

    Ivan,

    This bonding may help but there is still a high chance for oscillation. If for some reason they want to use the ONET8501T then they should consider the ONET8531T instead. The ONET8531T is the exact same part as the ONET8501T except the transimpedace is lower.

    The ONET8551T is a different TIA design compared to the ONET8501T/8531T although it is similar.

    Regards,

    Alex.