How to avoid kickback noise in a dynamic comparator?

[helna]

hI
we are designing a 7 bit flash ADC using dual-tail dynamic comparator. our common mode ref voltage is 600mV.
but our comparator is showing an offset of a few mV.
is it due to kickback noise?
how to remove it?
the comparators at the top and bottom end (among 127 comparators) are working well. the middle ones are showing some trouble.
thanks for your time.

 

[ducvilla]

Hi helna!

Actually, kickback noise can make offset to your circuit as u mentioned.
To remove it, you can read some techniques in some following papers (i think they are the best for your circuit):
1. Kickback Noise Reduction Techniques for CMOS Latched Comparators - Pedro M. Figueiredo.
2. A Low-Kickback-Noise Latched Comparator for High-Speed Flash Analog-to-Digital Converters - Proceedings of ISCIT2005

As far as i know, to reduce the kickback noise, you should isolate the couple pair and generative nodes of comparator, u can think a little bit about that, u will find out the solution!

Hope this help!

 

[helna]

Hi helna!

Actually, kickback noise can make offset to your circuit as u mentioned.
To remove it, you can read some techniques in some following papers (i think they are the best for your circuit):
1. Kickback Noise Reduction Techniques for CMOS Latched Comparators - Pedro M. Figueiredo.
2. A Low-Kickback-Noise Latched Comparator for High-Speed Flash Analog-to-Digital Converters - Proceedings of ISCIT2005

As far as i know, to reduce the kickback noise, you should isolate the couple pair and generative nodes of comparator, u can think a little bit about that, u will find out the solution!

Hope this help!

thanks for a quick response..
if you can, please post one of the above above mentioned papers. [A Low-Kickback-Noise Latched Comparator for High-Speed Flash Analog-to-Digital Converters - Proceedings of ISCIT 2005].
we are not able download it.
thank you.

 

[onmyphd]

Following the line of ducvilla, here is another suggestion:

Daniel Schinkel et. al,A Double-Tail Latch-Type Voltage Sense Amplifier with 18ps Setup+Hold Time, 2007

It has one stage for the diff pair and another for the regenerative stage. The diff pair has low tail current, thus low slew rate, which reduces kickback noise. The other stage can be driven by a large current for a fast regeneration.