V

+

GND

V

+

2.048V

GND

INP

INN

HYSTP

HYSTN

OUT

1.47 k:

1%

1 M:

1%

+

-

+

-

1 M:

1%

4.91 k:

1%

1 M:

1

IL

REF

REF

1

2

1

IH

REF

REF

1

2

R

V

V

V

R

R

R

V

V

V

R

R

æ

ö

=

-

ç

÷

+

è

ø

æ

ö

=

+

ç

÷

+

è

ø

LMP7300

www.ti.com

SNOSAT7G – AUGUST 2007 – REVISED OCTOBER 2015

Feature Description (continued)

7.3.3 Hysteresis

False triggering on noise coupled into the signal path is a common problem for comparator based threshold

detectors. One of the most effective solutions is to add hysteresis. Hysteresis is a circuit signal path

characteristic where an amplitude delay is introduced to the normal input. Positive hysteresis forces the signal to

pass the normal switch point before the output makes a low to high transition while negative hysteresis does the

opposite. This is a memory effect. The comparator behaves differently based on which direction the signal is

going.

The LM7300 has been designed with a unique way of introducing hysteresis. The set points are completely

independent of each other, the power supply, and the input or output conditions. The HYSTP pin sets positive

hysteresis and the HYSTN pin sets the negative hysteresis in a simple way using two resistors. The pins can be

tied together for the same hysteresis or tied to separate voltage taps for asymmetric hysteresis, or tied to the

reference for no hysteresis. When the precision reference is used to drive the voltage tap resistor divider precise,

stable threshold levels can be obtained. The maximum recommended hysteresis is about 130 mV. This places

negative input to keep the output off when the signal is above and on when it goes below this level. For a

(1)

Figure 12. Typical Micropower Application to Set Asymmetric Positive and

Negative Hysteresis of

−10 mV, 3 mV

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