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APPLICATION INFORMATION

BOARD LAYOUT

TLV3492

V

IN

V

OUT

0.01 µF

V

REF

10 µF

V+

SETTING REFERENCE VOLTAGE

EXTERNAL HYSTERESIS

HYST

1

2

V

R1

V

R

R

+

´

=

+

TLV3492

V

IN

V

OUT

V

HYST

=0.38V

V+

5V

V

REF

R

1

39kΩ

R

2

560kΩ

TLV3491A-EP, TLV3492A-EP, TLV3494A-EP

SGDS035 – DECEMBER 2007

The TLV349x family of comparators features rail-to-rail input and output on supply voltages as low as 1.8 V. The

push/pull output stage is optimal for reduced power budget applications and features no shoot-through current.

Low supply voltages, common-mode input range beyond supply rails, and a typical supply current of 0.8

µA

make the TLV349x family an excellent candidate for battery-powered applications with single-cell operation.

Figure 1 shows the typical connections for the TLV349x. To minimize supply noise, power supplies should be

capacitively decoupled by a 0.01

µF ceramic capacitor in parallel with a 10 µF 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 TLV3492

It is important to use a stable reference when setting the transition point for the TLV349x. The REF1004 provides

a 1.25-V reference voltage with low drift and only 8

µA of quiescent current.

Comparator inputs have no noise immunity within the range of specified offset voltage (±15 mV). 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 ±15 mV. To prevent multiple switching within the

comparator threshold of the TLV349x, external hysteresis may be added by connecting a small amount of

feedback to the positive input. Figure 2 shows a typical topology used to introduce hysteresis, described by the

equation:

threshold region, thereby reducing sensitivity to noise.

Figure 2. Adding Hysteresis to the TLV3492

Copyright © 2007, Texas Instruments Incorporated

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Product Folder Link(s): TLV3491A-EP TLV3492A-EP TLV3494A-EP