FD7745T Pletronics, Inc., FD7745T Datasheet - Page 5

• Manufacturer Part Number: FD7745T
• Description: Fd7t Series Multi-output Cmos Clock Oscillator
• Manufacturer: Pletronics, Inc.

PLL Multipliers
Spread Spectrum
Divider Section
The dividers add very little jitter to the output signals.
Multiplexers
There are up to 4 each independent PLL Multipliers and these can multiply the Reference Oscillator
frequency from 1 (bypass mode) to any value that is <=230MHz (the lowest frequency is the Reference
Oscillator frequency).
Each of the PLL Multipliers can have two setup options, 0 or 1, depending on which option is chosen
and set by the Sx control signals and the user’s definitions are stored in eePROM.
Each PLL has its individual Spread Spectrum (SS) function that can be enabled. This permits the
modulation of the output frequency by a user-set amount. The modulation can be centered on the
output frequency or down side only. Which of the 1 of 8 SS settings is being used is set by the Sx input
and the user definition. The value is a percentage of the output frequency that will be modulated.
The dividers operate on the output of the PLLs. There are two dividers on each PLL that divide by 1
through 127, the value is user defined. There is only 1 setting allowed per divider. These are not set by
the Sx input state.
MUX #1 selects the input to the Divider #1, this can be the reference oscillator signal or the output from
PLL Multiplier #1. MUX #2 through MUX #7 connect various divider outputs to the output buffers.
The device can make only one of the setting of connections shown in the block diagram (only one
pattern stored in eePROM).
www.pletronics.com
SS Option
0
1
2
3
4
5
6
7
Down Side Modulation
-0.25%
-0.50%
-0.75%
-1.00%
-1.25%
-1.50%
-2.00%
No SS
425-776-1880
FD7T Series Multi-Output
Centered Modulation
CMOS Clock Oscillator
+ _ 0.25%
+ _ 0.50%
+ _ 0.75%
+ _ 1.00%
+ _ 1.25%
+ _ 1.50%
+ _ 2.00%
No SS
May 2008
5