Rainbow Electronics MAX31D80 - Manual (Page 6)

Spread-Spectrum Clock Generators
MAX31C80/MAX31D80
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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