is it ok to connect the comparator inputs DIRECTLY to the dac outputs? If we do not care about jitter?
The DAC outputs are designed to provide sufficient common mode range to comparator input when dc coupled to one another. The internal comparator has an common-mode input range of 1.3 V to 1.8 V. So, if you dc couple the DAC outputs to the comparator with or without filtering it should switch the comparator. However, you'll have excessive jitter without filtering per Sitti's response. Hope this helps.
The AD9952 includes an on-chip comparator for applications that require a square wave signal. It is still better to place a filter between the output of the DAC and the input of the comparator to further suppress the effects of aliased images.
You might like to refer to this application note AN-837 which documents filter design in details and might give some useful tips.
Well, WE DO have 2 stages of active differential low pass filters after AD9952!! And we have LVDS comparator after the filter as well.
But as the onchip comparator exists, we wanted to use that too by direct connection to the non filtered outputs, so the question was only if direct connection without DC block capacitors is ok or not.
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