EVAL-CONTROLBRD2 AD [Analog Devices], EVAL-CONTROLBRD2 Datasheet - Page 23

• Manufacturer Part Number: EVAL-CONTROLBRD2
• Description: Differential Input, 1MSPS, 12-Bit ADC in ?SO-8 and S0-8
• Manufacturer: AD [Analog Devices]

PRELIMINARY TECHNICAL DATA
AD7450
APPLICATION HINTS
Grounding and Layout
The printed circuit board that houses the AD7450 should
be designed so that the analog and digital sections are
separated and confined to certain areas of the board. This
facilitates the use of ground planes that can be easily sepa-
rated. A minimum etch technique is generally best for
ground planes as it gives the best shielding. Digital and
analog ground planes should be joined in only one place
and the connection should be a star ground point estab-
lished as close to the GND pin on the AD7450 as
possible.
Avoid running digital lines under the device as
this will couple noise onto the die. The analog ground
plane should be allowed to run under the AD7450 to
avoid noise coupling. The power supply lines to the
AD7450 should use as large a trace as possible to provide
low impedance paths and reduce the effects of glitches on
the power supply line.
Fast switching signals like clocks should be shielded with
digital ground to avoid radiating noise to other sections
of the board, and clock signals should never run near the
analog inputs. Avoid crossover of digital and analog sig-
nals. Traces on opposite sides of the board should run at
right angles to each other. This will reduce the effects of
feedthrough
through the board.
A microstrip technique is
by far the best but is not always possible with a double-
sided board.
In this technique the component side of the board is dedi-
cated to ground planes while signals are placed on the
solder side.
Good decoupling is also important.
All analog supplies
should be decoupled with 10µF tantalum capacitors in
parallel with 0.1µF capacitors to GND.
To achieve the
best from these decoupling components, they must be
placed as close as possible to the device.
EVALUATING THE AD7450 PERFORMANCE
The recommended layout for the AD7450 is outlined in
the evaluation board for the AD7450.
The evaluation
board package includes a fully assembled and tested evalu-
ation board, documentation and software for controlling
the board from a PC via the EVALUATION BOARD
CONTROLLER.
The EVALUATION BOARD CON-
TROLLER can be used in conjunction with the AD7450
evaluation board, as well as many other Analog Devices’
evaluation boards ending with the CB designator, to dem-
onstrate/evaluate the ac and dc performance of the
AD7450.
The software allows the user the perform ac (fast Fourier
Transform) and dc (Histogram of codes) tests on the
AD7450.
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REV. PrJ