Stand-alone regenerative latched comparators

Binderman

on Jan 9, 2017

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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Binderman
on Jan 13, 2017 5:38 PM
I agree that at the extreme high-speed side of the application spectrum, it will probably be difficult to design a usefull standalone component because of parasitics that are much more dominant then what would be the case on-chip.

But that's not necessarily the field of application for such a component.

A typical ultra low power linear comparator that draws 1uA of quiescent current from its supply, has a ballpark propagation delay in the tens of microseconds. Very nice for low power battery operated or energy harvesting type of applications, but hardly usefull if you need to sample the input at speeds higher than a few tens of kHz.

A typical 100uA Iq comparator with a Tp of say 40ns would do the job, allowing for sample speeds well into the MHz range, but can become a significant battery drain.

In such applications a regenerative comparator could give you the best of both worlds, and in this domain of relatively low speed they wouldn't need be so "bleeding edge" technology.

Paul

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Binderman
on Jan 13, 2017 5:38 PM
I agree that at the extreme high-speed side of the application spectrum, it will probably be difficult to design a usefull standalone component because of parasitics that are much more dominant then what would be the case on-chip.

But that's not necessarily the field of application for such a component.

A typical ultra low power linear comparator that draws 1uA of quiescent current from its supply, has a ballpark propagation delay in the tens of microseconds. Very nice for low power battery operated or energy harvesting type of applications, but hardly usefull if you need to sample the input at speeds higher than a few tens of kHz.

A typical 100uA Iq comparator with a Tp of say 40ns would do the job, allowing for sample speeds well into the MHz range, but can become a significant battery drain.

In such applications a regenerative comparator could give you the best of both worlds, and in this domain of relatively low speed they wouldn't need be so "bleeding edge" technology.

Paul

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