Datasheet

TLV3491, 3492, 3494
SBOS262D
7
www.ti.com
APPLICATIONS INFORMATION
The TLV349x family of comparators features rail-to-rail input
and output on supply voltages as low as 1.8V. The push-pull
output stage is optimal for reduced power budget applica-
tions and features no shoot-through current. Low supply
voltages, common-mode input range beyond supply rails,
and a typical supply current of 0.8µA make the TLV349x
family an excellent candidate for battery-powered applica-
tions with single-cell operation.
BOARD LAYOUT
Figure 1 shows the typical connections for the TLV349x. To
minimize supply noise, power supplies should be capaci-
tively decoupled by a 0.01µF ceramic capacitor in parallel
with a 10µF electrolytic capacitor. Comparators are very
sensitive to input noise. Proper grounding (use of ground
plane) will help maintain specified performance of the TLV349x
family.
FIGURE 1. Basic Connections of the TLV349x.
FIGURE 2. Adding Hysteresis to the TLV349x.
SETTING REFERENCE VOLTAGE
It is important to use a stable reference when setting the
transition point for the TLV349x. The REF1004 provides a
1.25V reference voltage with low drift and only 8µA of
quiescent current.
EXTERNAL HYSTERESIS
Comparator inputs have no noise immunity within the range
of specified offset voltage (±15mV). For noisy input signals,
the comparator output may display multiple switching as
input signals move through the switching threshold. The
typical comparator threshold of the TLV349x is ±15mV. To
prevent multiple switching within the comparator threshold of
the TLV349x, external hysteresis may be added by connect-
ing a small amount of feedback to the positive input. Figure
2 shows a typical topology used to introduce hysteresis,
described by the equation:
V
VR
RR
HYST
=
×
+
+
1
12
V
HYST
will set the value of the transition voltage required to
switch the comparator output by increasing the threshold
region, thereby reducing sensitivity to noise.
TLV349x
V
IN
V
OUT
0.01µF
V
REF
10µF
V+
TLV349x
V
IN
V
OUT
V
HYST
= 0.38V
V+
5.0V
V
REF
R
1
39kΩ
R
2
560kΩ