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Stand-alone regenerative latched comparators

Hello all,

My question is about regenerative latched comparators.

I'm not sure if I posted this question in the correct forum, but since I know that these circuit topologies are frequently used inside modern A/D converters, I thought there might be some experts here who can shine a light on this.

My question is not  related to a specific part number but I was wondering why regenerative latched comparators are not offered as discrete parts by any manufacturer.

As much as they are indispensable in modern ADC architectures , they would make for a killer component in many mixed signal applications where high speed analog comparing and low power are key requirements. The speed to power ratio could be vastly improved for any time-discrete design, where there is now no other alternative than to use a power hungry linear comparator. Such a component would be a perfect supplement to modern ultra low power logic families and with only 6 pins needed could be housed in similarly small packages.

Is there a technical reason why such components don't exist or is there just no market for them?

Just wondering......

Regards,

Paul Beijer

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  • Hi Harry,

    Thanks for your reply, I appreciate.

    You maybe right about market demand. That's for the marketeers to judge. Maybe availability could fuel demand.

    I only know that I ran into the problem several times and ended up using a micro-power linear comparator followed by a D-flipflop to realize the same function. That burdened me with an awkward trade-off between quiescent current and speed. A regenerative comparator would have a far better figure of merit in that respect, since it uses no static power, only dynamic. I figured, I may not be the only one confronted with this dilemma. 

    I've used home-made regenerative comparators in my designs that I built using matched mosfet arrays and that's ok for prototyping and proofs of principle. Compared to the comparator/flipflop solution the trade-off improved by at least an order of magnitude. But for actual production it's far too costly and bulky and package parasitics make it difficult to get the input offset voltage within an acceptable range without factory adjustments.

    As for your argument of system integration I don't quite agree. That reasoning holds for many small scale integrated parts like simple op-amps, comparators, logic etc. and ultimately even for discretes. They all can be integrated into more complex IC's. Still there is a substantial market for them because many designs require tweaks of the standard applications. Or for new applications or circuit topologies where no standard IC solution fits the bill, and one has to invent the wheel themselves.

    Paul

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Reply
  • Hi Harry,

    Thanks for your reply, I appreciate.

    You maybe right about market demand. That's for the marketeers to judge. Maybe availability could fuel demand.

    I only know that I ran into the problem several times and ended up using a micro-power linear comparator followed by a D-flipflop to realize the same function. That burdened me with an awkward trade-off between quiescent current and speed. A regenerative comparator would have a far better figure of merit in that respect, since it uses no static power, only dynamic. I figured, I may not be the only one confronted with this dilemma. 

    I've used home-made regenerative comparators in my designs that I built using matched mosfet arrays and that's ok for prototyping and proofs of principle. Compared to the comparator/flipflop solution the trade-off improved by at least an order of magnitude. But for actual production it's far too costly and bulky and package parasitics make it difficult to get the input offset voltage within an acceptable range without factory adjustments.

    As for your argument of system integration I don't quite agree. That reasoning holds for many small scale integrated parts like simple op-amps, comparators, logic etc. and ultimately even for discretes. They all can be integrated into more complex IC's. Still there is a substantial market for them because many designs require tweaks of the standard applications. Or for new applications or circuit topologies where no standard IC solution fits the bill, and one has to invent the wheel themselves.

    Paul

    --

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