AD9879BS Analog Devices Inc, AD9879BS Datasheet - Page 29

• Manufacturer Part Number: AD9879BS
• Description: IC FRONT-END MIXED-SGNL 100-MQFP
• Manufacturer: Analog Devices Inc

Specifications of AD9879BS

• Rohs Status: RoHS non-compliant
• Number Of Bits: 12
• Number Of Channels: 5
• Power (watts): 587mW
• Voltage - Supply, Analog: 3.3V
• Voltage - Supply, Digital: 3.3V
• Package / Case: 100-MQFP, 100-PQFP

GROUND PLANES
In general, if the component placing guidelines discussed in the
Component Placement section can be implemented, it is best to
have at least one continuous ground plane for the entire board.
All ground connections should be made as short as possible.
This results in the lowest impedance return paths and the
quietest ground connections.
If the components cannot be placed in a manner that keeps the
high frequency ground currents from traversing under the
MxFE and analog components, it may be necessary to put
current steering channels into the ground plane to route the
high frequency currents around these sensitive areas. These
current steering channels should be made only when and where
necessary.
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SIGNAL ROUTING
The digital Rx and Tx signal paths should be kept as short as
possible. Also, these traces should have a controlled impedance
of about 50 Ω. This prevents poor signal integrity and the high
currents that can occur during undershoot or overshoot caused
by ringing. If the signal traces cannot be kept shorter than
approximately 1.5 inches, then series termination resistors
(33 Ω to 47 Ω) should be placed close to all signal sources. It is
advisable to series terminate all clock signals at their source
regardless of trace length.
The receive (I IN, Q IN, and RF IN) signals are the most
sensitive signals on the entire board. Careful routing of these
signals is essential for good receive path performance. The Rx±
signals form a differential pair and should be routed together as
a pair. By keeping the traces adjacent to each other, noise
coupled onto the signals appears as common-mode and is
largely rejected by the MxFE receive input. Keeping the driving
point impedance of the receive signal low and placing any low-
pass filtering of the signals close to the MxFE further reduces
the possibility of noise corrupting these signals.
AD9879