General-Purpose, Low-Voltage,

Single/Dual/Quad, Tiny-Pack Comparators

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7

Detailed Description

The LMX331/LMX393/LMX339 are single/dual/quad,

low-cost, general-purpose comparators. They have a

single-supply operating voltage of 1.8V to 5V. The com-

mon-mode input range extends from -0.1V below the

negative supply to within 0.7V of the positive supply.

They require approximately 60µA per comparator with

a 5V supply and 40µA with a 2.7V supply.

The LMX331H/LMX393H/LMX339H have 2mV of hys-

teresis for noise immunity. This significantly reduces the

chance of output oscillations even with slow-moving

input signals. The LMX331/LMX393/LMX339 and

LMX331H/LMX393H/LMX339H are ideal for automotive

applications because they operate from -40

°C to

+125

°C (see Typical Operating Characteristics).

Applications Information

Hysteresis

Many comparators oscillate in the linear region of oper-

ation because of noise or undesired parasitic feed-

back. This tends to occur when the voltage on one

input is equal or very close to the voltage on the other

input. The LMX331H/LMX393H/LMX339H have internal

hysteresis to counter parasitic effects and noise.

The hysteresis in a comparator creates two trip points:

one for the rising input voltage and one for the falling

input voltage (Figure 1). The difference between the trip

points is the hysteresis. When the comparator's input

voltages are equal, the hysteresis effectively causes

one comparator input to move quickly past the other,

thus taking the input out of the region where oscillation

occurs. This provides clean output transitions for noisy,

slow-moving input signals.

Additional hysteresis can be generated with two resis-

tors, using positive feedback (Figure 2). Use the follow-

ing procedure to calculate resistor values:

OUT

IN-

THRESHOLDS

IN+

HYSTERESIS

BAND

Figure 1. Threshold Hysteresis Band (Not to Scale)

PIN

LMX331

LMX393

LMX339

NAME

FUNCTION

1

—

—

IN+

Noninverting Input

2

4

12

Negative Supply (Connect to GND)

3

—

—

IN-

Inverting Input

4

—

—

OUT

Comparator Output (Open-Drain)

5

Positive Supply

—

1

2

OUTA

Comparator A Output (Open-Drain)

—

7

1

OUTB

Comparator B Output (Open-Drain)

—

2

4

INA-

Comparator A Inverting Input

—

3

5

INA+

Comparator A Noninverting Input

—

5

7

INB+

Comparator B Noninverting Input

—

6

6

INB-

Comparator B Inverting Input

—

—

8

INC-

Comparator C Inverting Input

—

—

9

INC+

Comparator C Noninverting Input

—

—

10

IND-

Comparator D Inverting Input

—

—

11

IND+

Comparator D Noninverting Input

—

—

13

OUTD

Comparator D Output (Open-Drain)

—

—

14

OUTC

Comparator C Output (Open-Drain)

Pin Description