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MAX9107

25ns, Dual/Quad/Single, Low-Power, TTL Comparators

Maxim Integrated 

MAX9107/MAX9108/MAX9109

25ns, Dual/Quad/Single, Low-Power,

TTL Comparators

Pin Description

MAX9107

1

2

3

7

6

5

—

—

—

—

—

—

—

—

—

8

4

—

—

PIN

MAX9108

MAX9109

SC70/SOT23

SO

1

—

—

2

—

—

3

—

—

7

—

—

6

—

—

5

—

—

8

—

—

9

—

—

10

—

—

14

—

—

13

—

—

12

—

—

—

1

7

—

3

2

—

4

3

4

6

1

11

2

6

—

5

5

—

—

4, 8

NAME

FUNCTION

OUTA

INA-

INA+

OUTB

INB-

INB+

OUTC

INC-

INC+

OUTD

IND-

IND+

OUT

IN+

IN-

VCC

GND

LE

N.C.

Channel A Output

Channel A Inverting Input

Channel A Noninverting Input

Channel B Output

Channel B Inverting Input

Channel B Noninverting Input

Channel C Output

Channel C Inverting Input

Channel C Noninverting Input

Channel D Output

Channel D Inverting Input

Channel D Noninverting Input

Output

Noninverting Input

Inverting Input

Positive Supply

Ground

Latch Enable. The latch is transparent when LE is low.

No Connection. Not internally connected.

Detailed Description

Timing

Noise or undesired parasitic AC feedback cause most

high-speed comparators to oscillate in the linear region

(i.e., when the voltage on one input is at or near the

voltage on the other input). The MAX9107/MAX9108/

MAX9109 eliminate this problem by incorporating an

internal hysteresis of 2mV. When the two comparator

input voltages are equal, hysteresis effectively causes

one comparator input voltage to move quickly past

the other, thus taking the input out of the region where

oscillation occurs. Standard comparators require that

hysteresis be added through the use of external resis-

tors. The MAX9107/MAX9108/MAX9109’s fixed internal

hysteresis eliminates these resistors. To increase hyster-

esis and noise margin even more, add positive feedback

with two resistors as a voltage divider from the output to

the noninverting input.

Adding hysteresis to a comparator creates two trip points:

one for the input voltage rising and one for the input

voltage falling (Figure 1). The difference between these

two input-referred trip points is the hysteresis. The

average of the trip points is the offset voltage.

Figure 1 illustrates the case where IN- is fixed and IN+ is

varied. If the inputs were reversed, the figure would look

the same, except the output would be inverted.

The MAX9109 includes an internal latch, allowing the

result of a comparison to be stored. If LE is low, the latch

is transparent (i.e., the comparator operates as though

the latch is not present). The state of the comparator

output is latched when LE is high (Figure 2).

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