Dual, Ultra-Fast ECL-Output Comparator

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3

Note 2:

Not tested, guaranteed by design.

Note 3:

VIN = 100mV, VOD = 10mV.

Figure 2. As a high-speed receiver, the MAX9687 is capable of

processing signals in excess of 600MHz. Figure 2 is a 100MHz

Figure 1. High-speed receiver application with 50

Ω input and out-

put termination. With this configuration, in which a ground plane and

microstrip PC board was used, the minimum slew rate for clean out-

put switching is 1.6V/µs. For sine-wave inputs, this implies a mini-

0V

-0.9V

-1.7V

OUTPUT

INPUT

OUTPUT

500mV/div

INPUT

20mV/div

2ns/div

-2V

50

Ω

50

Ω

50

Ω

50

Ω

LE

SWITCHING CHARACTERISTICS

1.4

1.9

PARAMETER

SYMBOL

MAX9687C/E

MIN

TYP

MAX

UNITS

CONDITIONS

E RMS =

Slew Rate

2f

2

π

1.6

2.2

1.4

1.9

MAX9687M

MIN

TYP

MAX

1.4

1.9

1.7

2.6

1.4

1.9

Input to Output High

(Notes 2, 3)

ns

1.9

2.6

Input to Output Low

(Notes 2, 3)

1.3

1.8

1.4

2.0

1.3

1.8

ns

1.6

2.2

1.3

1.8

1.5

2.0

1.7

2.6

Latch-Enable to Output Low

(Notes 2, 3)

ns

1.6

1.9

1.4

1.8

Latch-Enable to Output High

(Notes 2, 3)

ns

3.0

2.0

Latch-Enable Pulse Width (Note 2)

0.5

1.0

Minimum Setup Time

0.5

1.0

3.0

2.0

0.5

1.0

Minimum Hold Time

0.5

1.0

ns

__________Applications Information

Layout

Because of the MAX9687’s large gain-bandwidth charac-

teristic, special precautions need to be taken if its high-

speed capabilities are to be used. A PC board with a

ground plane is mandatory. Mount all decoupling capaci-

tors as close to the power-supply pins as possible, and

process the ECL outputs in microstrip fashion, consistent

with the load termination of 50

Ω to 120Ω. For low-imped-

ance applications, microstrip layout at the input may also

be helpful. Pay close attention to the bandwidth of the

decoupling and terminating components. Chip compo-

nents can be used to minimize lead inductance.

Input Slew-Rate Requirement

As with all high-speed comparators, the high gain-

bandwidth product of these devices creates oscillation

problems when the input traverses through the linear

region. For clean switching without oscillation or steps

in the output waveform, the input must meet certain