LMH7220: LMH7220 Hysteresis

Hi Aramis,

this application note shows how to proceed:

www.ti.com/lit/ug/snoa478a/snoa478a.pdf

Kai

Kai,

Thank you for the answer.

Why do I need hysteresis on both inputs?

Hi Aramis,

to preserve the symmetry.

Kai

In my application the non-inverting side is connected to a reference and the inverting side is the changing signal.
Way I see it, hysteresis is required in the reference input only.
Do I need hysteresis on both inputs in my case?

Hello Aramis,

The inputs are single ended - so the hysteresis feedback needs to come from just one of the outputs.

From the non-inverting output (Q) to the non-inverting (+) input,

 or,

From the inverting output (/Q) to the inverting input (-).

But not both!

So the standard theory and equations for hysteresis apply. However, the LVDS outputs complicate things. Remember that the LVDS outputs have a ±325mV swing around 1.2V (1.0375V to 1.3625V), so you must use these numbers for the output VOL and VOH in the calculations.

For more info on hysteresis, see the TI Precision Labs on comparators (Section 14.2):

 TI Precision Labs - Op Amps: Comparator Applications