Unfortunately because of new architecture which we have considered for comparator, we have considerable kickback noise and the amount of input capacitors of comparator is too high. So the resistor ladder is not stable and it decrease gradually. So, I need an architecture or any idea for making it more stable.
Regards,
Mehdi
Hello,
knowing nothing about your current (and previous) architecture (aka topology), we have to make an educated guess... BTW: the term "kickback noise" is no denomination I ever saw, so I have to interpret.
So - my guess:
Could it be that you swapped from comparators to comparators with hysteresis ?
If so - if the resistor ladder isn't very low impedance compared to the hysteresis feedback resistance (especially important in the "middle" of the ladder where impedance is at its maximum), you will not be able to get rid of the problem. As it is physically impossible. Adding capacitance does not help - just slow down your "flash" ADC. The same applies when increasing the feedback resistance - maybe to a lower extend.
What would help (not exactly a 'cheap' solution): "isolate" the resistor ladder by buffers (1 for each node) to prevent the feedback from feeding back into the ladder.
Wish you success
Unfortunately the answer did not help me that much. The problem is my input capacitors and resistors of the comparator. So, they effect on the resistor ladder considerably.
Physics is always working against us :(
So my assumption about hysteresis seems to have been correct.
Can you supply schematics of "old" and "new" - including values and your "input capacitors". Regarding the capacitors I currently have absolutely no idea what they might or might not have to do with your problem.
Regards
Unfortunately I Can not put it here. Because it is novel idea. Do you have any idea about T-Switch? I need some switches except transmission gate that the effects would be less on the resistor ladder.
Switches ? Tend to be 2-way. And I cannot see how you could control them.
I already asked: would the effects vanish if you'd implement an amplifier for every ladder node ? (Not that this would be practical - just to get the idea whether your problem is caused only by hysteresis feedback or whether something else is looming.)
Would it work better when the comparators' resistors were higher by the factor of 10 whilst the resistor ladder consisted of 1-Ohm resistors ?
it is obvious that if I increase the resistors value... everything will destroy...
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