Datasheet

V
IN1
=
V
REF
(R
1
+ R
2
)
R
2
'V
A
=
+V
CC
R
1
R
2
R
1
R
2
+ R
1
R
3
+ R
2
R
3
LPV7215
SNOSAI6I –SEPTEMBER 2005–REVISED APRIL 2013 www.ti.com
INVERTING COMPARATOR WITH HYSTERESIS
The inverting comparator with hysteresis requires a three resistor network that is referenced to the supply voltage
V
+
of the comparator as shown in Figure 34. When V
IN
at the inverting input is less than V
A
, the voltage at the
non-inverting node of the comparator (V
IN
< V
A
), the output voltage is high (for simplicity assume V
O
switches as
high as V
+
). The three network resistors can be represented as R
1
//R
3
in series with R
2
.
The lower input trip voltage V
A1
is defined as
V
A1
= V
CC
R
2
/ ((R
1
//R
3
) + R
2
)
When V
IN
is greater than V
A
, the output voltage is low or very close to ground. In this case the three network
resistors can be presented as R
2
//R
3
in series with R
1
.
The upper trip voltage V
A2
is defined as
V
A2
= V
CC
(R
2
//R
3
) / ((R
1
+ (R
2
//R
3
)
The total hysteresis provided by the network is defined as ΔV
A
= V
A1
- V
A2
Figure 34. Inverting Comparator with Hysteresis
NON-INVERTING COMPARATOR WITH HYSTERESIS
A non-inverting comparator with hysteresis requires a two resistor network, and a voltage reference (V
REF
) at the
inverting input. When V
IN
is low, the output is also low. For the output to switch from low to high, V
IN
must rise up
to V
IN1
where V
IN1
is calculated by.
As soon as V
O
switches to V
CC
, V
A
will step to a value greater than V
REF
, which is given by
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