ADV7192 datasheet(45/69 Pages) AD

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ADV7192

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APPENDIX 1

BOARD DESIGN AND LAYOUT CONSIDERATIONS

The ADV7192 is a highly integrated circuit containing both

precision analog and high-speed digital circuitry. It has been

designed to minimize interference effects on the integrity of the

analog circuitry by the high-speed digital circuitry. It is imperative

that these same design and layout techniques be applied to the

system level design such that high-speed, accurate performance

is achieved. The Recommended Analog Circuit Layout shows the

analog interface between the device and monitor.

The layout should be optimized for lowest noise on the ADV7192

power and ground lines by shielding the digital inputs and pro-

viding good decoupling. The lead length between groups of VAA

and GND pins should by minimized so as to minimize inductive

ringing.

Ground Planes

The ground plane should encompass all ADV7192 ground pins,

voltage reference circuitry, power supply bypass circuitry for

the ADV7192, the analog output traces, and all the digital signal

traces leading up to the ADV7192. This should be as substantial as

possible to maximize heat spreading and power dissipation on the

board.

Power Planes

The ADV7192 and any associated analog circuitry should have its

own power plane, referred to as the analog power plane (VAA). This

power plane should be connected to the regular PCB power plane

(VCC) at a single point through a ferrite bead. This bead should

be located within three inches of the ADV7192.

The metallization gap separating device power plane and board

power plane should be as narrow as possible to minimize the

obstruction to the flow of heat from the device into the general

board.

The PCB power plane should provide power to all digital logic

on the PC board, and the analog power plane should provide

power to all ADV7192 power pins and voltage reference circuitry.

Plane-to-plane noise coupling can be reduced by ensuring that

portions of the regular PCB power and ground planes do not

overlay portions of the analog power plane, unless they can be

arranged such that the plane-to-plane noise is common-mode.

Supply Decoupling

For optimum performance, bypass capacitors should be installed

using the shortest leads possible, consistent with reliable operation,

to reduce the lead inductance. Best performance is obtained

with 0.1

µF ceramic capacitor decoupling. Each group of V

pins on the ADV7192 must have at least one 0.1

µF decoupling

capacitor to GND. These capacitors should be placed as close as

possible to the device.

It is important to note that while the ADV7192 contains circuitry

to reject power supply noise, this rejection decreases with fre-

quency. If a high frequency switching power supply is used, the

designer should pay close attention to reducing power supply

noise and consider using a three-terminal voltage regulator for

supplying power to the analog power plane.

Digital Signal Interconnect

The digital inputs to the ADV7192 should be isolated as much as

possible from the analog outputs and other analog circuitry. Also,

these input signals should not overlay the analog power plane.

Due to the high clock rates involved, long clock lines to the

ADV7192 should be avoided to reduce noise pickup.

Any active termination resistors for the digital inputs should be

connected to the regular PCB power plane (VCC), and not the

analog power plane.

Analog Signal Interconnect

The ADV7192 should be located as close as possible to the output

connectors to minimize noise pickup and reflections due to

impedance mismatch.

The video output signals should overlay the ground plane, and

not the analog power plane, to maximize the high frequency power

supply rejection.

Digital inputs, especially pixel data inputs and clocking signals

should never overlay any of the analog signal circuitry and should

be kept as far away as possible.

For best performance, the outputs should each have a 300

Ω load

resistor connected to GND. These resistors should be placed as

close as possible to the ADV7192 so as to minimize reflections.

The ADV7192 should have no inputs left floating. Any inputs

that are not required should be tied to ground.

ADV7192 Datasheet(PDF) 45 Page - Analog Devices

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