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AD96687 Designing

Hi Friends,
I am interested in one of your high-speed dual-channel comparator AD96687 and I would like to use it in one of our projects.
We are not using the Latching function. so as per the datasheet, the Latch Enable pin should be Grounded Right?.
Even after completing the datasheet, I don't have a clear idea of the latching operation of the chip.
Can someone help me in solving this?

  • Hi Shibin,

    Now this circuit seems much better to me. But you're talking about your ECL logic. Do I understand correctly that you want to use some special logic on discrete components and connect it to this comparator?

    Because if you were using a standard ECL series, you wouldn't be asking these questions. This connects directly to each other.

    First, please draw a more detailed circuit where these two parts are connected to each other:

    Because I'm confused.



  • I don't understand whether you mean one of the Latch Enable inputs or the Comparator inputs to be grounded to disable the latching operation

    The "lower floor" of the internal circuit of this comparator is the logical part. Here's what it looks like:

    You can see that the logic input ground is interpreted as a logic level because the ground potential is higher than the Vr reference voltage. I hope this will clarify something for you

    The positive supply voltage is used by the analog comparator circuit itself. I understand this intuitively. Unfortunately, the Analog Devices application engineers don't participate in this discussion and can't tell if I'm right or wrong.

  • Thank You for your reply.
    The ECL I am using is single-ended not a differential and my doubt is can I use PECL with AD9687.
    Also, I have seen another chip  ADCMP551BRQZ of Analog Devices. Can I use this chip for my application?.

  • my doubt is can I use PECL with AD9687.

    PECL and ECL are mirror images of each other. In principle, this looks possible, but you should move the AD96687 output signals up, above the ground potential.

    Obviously, your cryptic single-ended logic has logical thresholds. There is a maximum voltage that will be reliably perceived as a logical 1 and there is a minimum voltage that will be reliably perceived as a logical 0.

    You have given very little information, and so far I can't say anything specific.