REV. B

AD9884A

–8–

PIN FUNCTION DESCRIPTIONS (Continued)

Pin Name

Function

ANALOG INTERFACE

REFOUT

Internal Reference Output

Output from the internal 1.25 V bandgap reference. This output is intended to drive relatively light loads. It can

drive the AD9884A Reference input directly, but should be externally buffered if it is used to drive other loads as

well. The absolute accuracy of this output is

±4%, and the temperature coefficient is ±50 ppm, which is adequate

for most AD9884A applications. If higher accuracy is required, an external reference may be employed. If an exter-

nal reference is used, tie this pin to ground through a 0.1

µF capacitor.

REFIN

Reference Input

The reference input accepts the master reference voltage for all AD9884A internal circuitry (+1.25 V

± 10%). It

may be driven directly by the REFOUT pin. Its high impedance presents a very light load to the reference source.

This pin should be bypassed to Ground with a 0.1

µF capacitor.

FILT

External Filter Connection

For proper operation, the pixel clock generator PLL requires an external filter. Connect the filter shown in Figure

10 to this pin. For optimal performance, minimize noise and parasitics on this node.

POWER SUPPLY

Main Power Supply

These pins supply power to the main elements of the circuit. It should be as quiet and filtered as possible.

Digital Output Power Supply

A large number of output pins (up to 52) switching at high speed (up to 140 MHz) generates a lot of power supply

minimize output noise transferred into the sensitive analog circuitry. If the AD9884A is interfacing with lower-

Clock Generator Power Supply

The most sensitive portion of the AD9884A is the clock generation circuitry. These pins provide power to the

clock PLL and help the user design for optimal performance. The designer should provide “quiet,” noise-free

power to these pins.

GND

Ground

The ground return for all circuitry on chip. It is recommended that the AD9884A be assembled on a single solid

ground plane, with careful attention to ground current paths. See the Design Guide for details.