AFE2126E BURR-BROWN [Burr-Brown Corporation], AFE2126E Datasheet - Page 11

• Manufacturer Part Number: AFE2126E
• Description: Dual HDSL/SDSL ANALOG FRONT END
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

LAYOUT
The analog front end of an HDSL system has two conflicting
requirements. It must accept and deliver moderately high
rate digital signals and it must generate, drive, and convert
precision analog signals. To achieve optimal system perfor-
mance with the AFE2126, both the digital and the analog
sections must be treated carefully in board layout design.
The power supply for the digital section of the AFE2126 can
range from 3.3V to 5V. This supply should be decoupled to
digital ground with ceramic 0.1 F capacitors placed as close
to DGND and DV
placed between pins 7 and 8, and the second capacitor,
between pins 41 and 42. Ideally, both a digital power supply
plane and a digital ground plane should run up to, and
underneath the digital pins of the AFE2126 (pins 1 through
6, and pins 43 through 48). However, DV
by a wide printed circuit board (PCB) trace. A digital ground
plane underneath all digital pins is strongly recommended.
DD
as possible. One capacitor should be
DD
may be supplied
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The remaining portion of the AFE2126 should be considered
analog. All AGND pins should be connected directly to a
common analog ground plane and all AV
connected to an analog 5V power plane. Both of these planes
should have a low impedance path to the power supply. The
analog power supply pins should be decoupled to analog
ground with ceramic 0.1 F capacitors placed as close to the
AFE2126 as possible. One 10 F tantalum capacitor should
also be used with each AFE2126 between the analog supply
and analog ground.
Ideally, all ground planes and traces, and all power planes
and traces should return to the power supply connector
before being connected together (if necessary). Each ground
and power pair should be routed over each other, should not
overlap any portion of another pair, and the pairs should be
separated by a distance of at least 0.25 inch (6mm). One
exception is that the digital and analog ground planes should
be connected together underneath the AFE2126 by a small
trace.
AFE2126
DD
pins should be
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