Spread-Spectrum Clock Generators

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Block Diagram

Pin Description

Pin Configuration

1

3

4

10

8

7

2

9

EP

5

6

TDFN

TOP VIEW

MAX31C80

MAX31D80

CRYSTAL

OSCILLATOR

PROGRAMMABLE

PLL WITH SPREAD

SPECTRUM

SPREAD-SPECTRUM

MAGNITUDE CONTROL

CLKOUT

XOUT

GND

X1

X2

SMSEL0

SMSEL1

8MHz TO 134MHz CLOCK

OR

8MHz TO 34MHz CRYSTAL

MAX31C80

MAX31D80

PIN

NAME

FUNCTION

1

X1

Crystal Drive/Clock Input. A crystal with

the proper loading is connected across

X1 and X2. Instead of a crystal, a clock

can be applied at the X1 input. If no

clock or crystal is present, then no clock

is output at either XOUT or CLKOUT.

2, 9

SMSEL0,

SMSEL1

Spread-Spectrum Magnitude Select.

These are three-state digital inputs

to determine the spread-spectrum

magnitude. Tables 1 and 2 provide

details for configuration of these pins for

down and center dither, respectively.

PIN

NAME

FUNCTION

3, 8

Supply Voltage

4, 7

GND

Ground

5

CLKOUT

Clock Output. Spread-spectrum-capable

digital output clock from the PLL.

6

XOUT

Crystal Buffered Output. Buffered digital

output of the input crystal or clock.

10

X2

Crystal Drive Output. A crystal with the

proper loading is connected across X1

and X2. If a clock is applied at the X1

input, then X2 should be left open circuit.

—

EP

Exposed Pad. Connect to GND.