EL4584CS datasheet(12/16 Pages) ELANTEC

12 / 16 page

EL4584C

Horizontal Genlock 4 FSC

PCB Layout Considerations

It is highly recommended that power and ground

planes be used in layout The oscillator and filter

sections constitute a feedback loop and thus care

must be taken to avoid any feedback signal influ-

encing the oscillator except at the control input

The entire oscillatorfilter section should be sur-

rounded by copper ground to prevent unwanted

influences from nearby signals

Use separate

paths for analog and digital supplies keeping the

analog (oscillator section) as short and free from

spurious signals as possible Careful attention

must be paid to correct bypassing Keep lead

lengths short and place bypass caps as close to

the supply pins as possible If laying out a PCB

to use discrete components for the VCO section

care must be taken to avoid parasitic capacitance

at the OSC pins 3 and 5 and FILTER out (pin

Remove ground and power plane copper

above and below these traces to avoid making a

capacitive connection to them It is also recom-

mended to enclose the oscillator section within a

shielded cage to reduce external influences on the

VCO as they tend to be very sensitive to ‘‘hand-

waving’’ influences the LC variety being more

sensitive than crystal controlled oscillators In

general the higher the operating frequency the

more important these considerations are

Self

contained VCXO or VCO modules are already

mounted in a shielding cage and therefore do not

require as much consideration in layout Many

crystal manufacturers publish informative litera-

ture regarding use and layout of oscillators which

should be helpful

EL4584CS Datasheet(PDF) 12 Page - Elantec Semiconductor