What minimum slew rate for ADCMP582 input for for good jitter (0.2 ps rms) ?
What minimum input sinewave amplitude for ADCMP582 for correct work?
As I understand on your synchronization schematic, you are trying to adjust the hysteresis by controlling the RDSon of VT2. If VT2 is operating at the cut-off region, there would be no issues since the hysteresis will only be at 1mV(approx. open) but when VT2 is in saturation the hysteresis will be around 70mV which might be the reason why you are encountering bad toggle on a 100mV signal. Kindly check on Figure 8. Hysteresis VS. R_HYS control resistor on the data sheet for reference.
I'm not seeing any issues on your second schematic and the ADCMP582 could handle a 1V/ns slew rate at its input with very at very low jitter.
We can approximate the typical slew rate of the ADCMP582 using the VOH, VOL, and rise/fall time specifications.
Slew Rate=(0.6*(VOH-VOL))/ tR;
Slew Rate is 6.32V/ns for VCCO=3.3V and @ 25C.
Ideally, the input signal should be greater than the input offset voltage to toggle the output from high to low or vice versa. VOS is typically 4mV @ 25C or 10mV over operating temperature.
May we ask about your circuit/application and why are you particularly interested on the slew rate and jitter performance of the ADCMP582?
I use two comaparators. First for sinchronization. I get bad jittter at 2GHz sinewave when input amplitude is less then 100 mV or i get bad toggle. It's why i ask you about minimum input amplitude.
2nd comaprator use for compare ramp 1V/ns total amplitude +/-2V. I want to be sure that i put to input a good slewrate ramp to get low jitter.
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