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LMH7322: High speed comparator LMH7322 hysteresis control

Martin Hu57
Prodigy 100 points
Part Number: LMH7322

I am going to design a circuit to control the hysteresis of the comparator  LMH7322 as the following circuit, but we found some comments on the datasheet page 23. It said “Connecting the RHYS pin to another voltage as provided by the RHREF pin is not covered in the resistor selection plot and the designer of such a circuit must be aware of abnormal behaviour.” My design is not connect the voltage reference to RHYS pin directly but through a 1K resistor, I hope it will not cause any abnormal behaviour. Also, how accuracy the hysteresis control can be achieved if you can give some estimation?

  • 0
    TI__Genius 15975 points

    Hi Martin,

    Would it be possible for you to re-attach your schematic? Looks like it did not go through while attaching.

    If I look at the hysteresis numbers below for RHYS = 0ohm and assume 4sigma variation from the mean(typ) of 50mV, the standard deviation (sigma) across parts would be +/- 6.25mV from the mean. I think this would be the worst case limit, since the hysteresis is the maximum for RHYS = 0ohm. For other RHYS resistor values as shown in Figure 16 of the datasheet, the hysteresis voltage is tighter (or smaller) and should give a much smaller standard deviation than +/-6.25mV from the mean. 

    Best Regards,

    Rohit