I need clarification regarding comparators with internal Hysteresis.

I have a comparator with internal Hysteresis “X” mv and I am using external feedback resistors to create a hysteresis of “Y” mv.

Will the total hysteresis be “X+Y” mv?

  • \$\begingroup\$ You might be able to figure out the resistance requried to achieve the internal hysteresis. Then put whatever external feedback resistor you want to use in parallel with that then use the parallel combination to re-calculate the hysteresis. But I'm not sure if that is valid since I don't know how internal hysteresis is implemented. \$\endgroup\$ – DKNguyen Mar 3 '20 at 4:34

From Maxim note:

Hysteresis is designed into most comparators, usually with a value of 5mV to 10mV. Internal hysteresis helps the comparator avoid oscillation due to small amounts of parasitic feedback. Though sufficient to prevent the comparator from self-oscillating, such internal hysteresis can easily be swamped by any external noise of greater amplitude. In that case, you can improve performance by adding hysteresis externally.

  • Assuming Y > X, then the system hysteresis will be Y mV only.
  • Assuming Y < X, then the system hysteresis will be X mV only.
  • \$\begingroup\$ Hi,If I am providing external hysteresis will it get added to internal Hysteresis or external hysteresis will override the internal Hystersis \$\endgroup\$ – Hari Mar 12 '20 at 6:09
  • 1
    \$\begingroup\$ It will not get added, bigger of the two will be active \$\endgroup\$ – User323693 Mar 12 '20 at 6:12

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