LM339LVDR datasheet(26/63 Pages) TI1

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8.2.1.1 Design Requirements

For this design, follow these design requirements:

• Alert (logic low output) when an input signal is less than 1.1 V

• Alert (logic low output) when an input signal is greater than 2.2 V

• Alert signal is active low

• Operate from a 3.3-V power supply

8.2.1.2 Detailed Design Procedure

Configure the circuit as shown in Figure 8-7. Connect VCC to a 3.3-V power supply and VEE to ground. Make R1,

R2 and R3 each 10-MΩ resistors. These three resistors are used to create the positive and negative thresholds

for the window comparator (VTH+ and VTH–).

With each resistor being equal, VTH+ is 2.2 V and VTH- is 1.1 V. Large resistor values such as 10-MΩ are used to

minimize power consumption. The resistor values may be recalculated to provide the desired trip point values.

The sensor output voltage is applied to the inverting and noninverting inputs of the two comparators. Using two

open-drain output comparators allows the two comparator outputs to be Wire-OR'ed together.

The respective comparator outputs will be low when the sensor is less than 1.1 V or greater than 2.2 V.

The respective comparator outputs will be high when the sensor is in the range of 1.1 V to 2.2 V (within the

"window"), as shown in Figure 8-8.

8.2.1.3 Application Curve

VTH+ = 2.2 V

VTH± = 1.1 V

VIN

OUT

Figure 8-8. Window Comparator Results

For more information, please see Application note SBOA221 "Window comparator circuit".

8.2.2 Square-Wave Oscillator

Square-wave oscillator can be used as low cost timing reference or system supervisory clock source.

100 pF

100 kŸ

VCC

100 kŸ

OUT

100 kŸ

Figure 8-9. Square-Wave Oscillator

TL331LV, TL391LV, LM393LV, LM339LV

SNOSDA4C – JUNE 2020 – REVISED MARCH 2023

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LM339LVDR Datenblatt(PDF) 26 Page - Texas Instruments