Rainbow-electronics MAX31D80 Manual de usuario descargar pdf (Pagina 6)

Spread-Spectrum Clock Generators

MAX31C80/MAX31D80

6 ______________________________________________________________________________________

Detailed Description

The MAX31C80/MAX31D80 modulate an input clock to

generate a center-dithered or down-dithered spread-

spectrum output. An 8MHz to 27MHz crystal or 8MHz

to 134MHz oscillator input is applied to the device. An

internal PLL dithers the output clock at a user-select-

able magnitude to produce a down-dithered or center-

dithered output clock. The output clock’s frequency is

programmable from 2MHz to 134MHz. The devices also

buffer the incoming clock and provide this output on a

separate pin.

Spread-Spectrum Dither Magnitude

The MAX31D80 can generate down-dithered magnitudes

up to -3%. The MAX31C80 can generate center-dithered

magnitudes up to P 1.5%. The desired magnitude is

selected using the input pins SMSEL1 and SMSEL0 as

shown in Tables 1 and 2. A power cycle is required after

each change of the dither magnitude for the changes to

take effect.

Table 1. Spread-Spectrum Mode and Magnitude Select (for Down Dither)

Table 2. Spread-Spectrum Mode and Magnitude Select (for Center Dither)

SMSEL1 SMSEL0

SPREAD-SPECTRUM MAGNITUDE

SELECTED (%)

SPREAD-SPECTRUM DITHER MODE

SELECTED

0 0 Spread-Spectrum Disabled

0 Unconnected 0 to -0.25

Down Dither

0 1 0 to -0.375

Unconnected 0 0 to -0.5

Unconnected Unconnected 0 to -0.75

Unconnected 1 0 to -1.0

1 0 0 to -1.5

1 Unconnected 0 to -2.0

1 1 0 to -3.0

SMSEL1 SMSEL0

SPREAD-SPECTRUM MAGNITUDE

SELECTED (%)

SPREAD-SPECTRUM DITHER MODE

SELECTED

0 0 Spread-Spectrum Disabled

0 Unconnected -0.25 to +0.25

Center Dither

0 1 -0.375 to +0.375

Unconnected 0 -0.5 to +0.5

Unconnected Unconnected -0.75 to +0.75

Unconnected 1 -1.0 to +1.0

1 0 -1.5 to +1.5

1 Unconnected N/A

1 1 N/A

1 2 3 4 5 6 7 8 9

MAX31C80/MAX31D80 1

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