GS4915_09 Datasheet, PDF (1/27 Pages) Gennum Corporation – ClockCleaner

GS4915 ClockCleaner™
Key Features
• 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
Applications
High definition video systems. Digital video recording,
playback, processing and display devices.
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.
GS4915 ClockCleaner™
Data Sheet
39145 - 5
June 2009
www.gennum.com
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