GS4915 ClockCleaner™
GS4915 Data Sheet
Key Features
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Reduces jitter for clocks of 148.5MHz,
148.5/1.001MHz, 74.25MHz, 74.25/1.001MHz and
27MHz
Output jitter as low as 20ps peak to peak
Automatic bypass mode for all other clock rates
Loop bandwidth adjustable as low as 2kHz
Output skew control
Input selectable as differential or single-ended
Both single-ended and differential outputs
Uses the GO1555 VCO
Small 6mm x 6mm 40-pin QFN package
Pb-free and RoHS compliant
Description
The GS4915 provides a low jitter clock output when fed
with an HD or SD video clock input. Other input clock
frequencies between 12MHz and 165MHz can be
automatically passed through to the GS4915 outputs.
An internal 2:1 mux allows the user to select between a
differential or single-ended (LVCMOS) input clock. Both
a single-ended LVCMOS- compatible and an
LVDS-compatible differential output are provided.
The GS4915 may operate in either auto or fixed
frequency mode. In auto mode, the device will
automatically clean the selected input clock if its
frequency is found to be one of the supported SD or HD
clock rates. In fixed mode, the user selects only one of
these frequencies to be cleaned.
In addition, the device allows the user to select between
auto or manual bypass operation. In autobypass mode,
the GS4915 will automatically bypass its cleaning stage
and pass the input clock signal directly to the output
whenever the device is unlocked, which includes the
case where the input frequency is something other than
the five frequencies supported. In manual bypass
mode, the input signal passes through directly to the
output.
The GS4915 can optionally double the output frequency
for 74.25MHz or 74.175MHz HD clocks in order to
provide optimal jitter performance of some serializers.
The GS4915 also provides the user with a 2-state skew
control. The output clocks produced by the device may
be advanced by ¼ of an output CLK period in order to
accommodate downstream setup and hold
requirements.
The GS4915 is designed to operate with the GO1555
VCO.
The GS4915 Clock Cleaner complements Gennum's
GS4911B Clock and Timing Generator for
implementing a video genlock solution. Whereas the
GS4911B itself cleans low-frequency jitter, the GS4915
is designed to clean primarily the higher frequency jitter
of clocks generated by the GS4911B.
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Applications
High definition video systems. Digital video recording,
playback, processing and display devices.
39145 - 3
November 2007
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