AD9880SLASHPCB datasheet(59/64 Pages) AD

59 / 64 page

AD9880

Rev. 0 | Page 59 of 64

Outputs (Both Data and Clocks)

Try to minimize the trace length that the digital outputs have to

drive. Longer traces have higher capacitance, which require

more current that causes more internal digital noise.

Shorter traces reduce the possibility of reflections.

Adding a series resistor of value 50 Ω to 200 Ω can suppress

reflections, reduce EMI, and reduce the current spikes inside of

the AD9880. If series resistors are used, place them as close as

possible to the AD9880 pins (although try not to add vias or

extra length to the output trace to move the resistors closer).

If possible, limit the capacitance that each of the digital outputs

drives to less than 10 pF. This can be easily accomplished by

keeping traces short and by connecting the outputs to only one

device. Loading the outputs with excessive capacitance increases

the current transients inside of the AD9880 and creates more

digital noise on its power supplies.

Digital Inputs

The digital inputs on the AD9880 were designed to work with

3.3 V signals, but are tolerant of 5.0 V signals. Therefore, no

extra components need to be added if using 5.0 V logic.

Any noise that enters the Hsync input trace can add jitter to the

system. Therefore, minimize the trace length and do not run

any digital or other high frequency traces near it.

AD9880/PCB 数据表(PDF) 59 Page - Analog Devices