AD9923 Analog Devices, AD9923 Datasheet - Page 59

• Manufacturer Part Number: AD9923
• Manufacturer: Analog Devices

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
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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