AD7339 Analog Devices, AD7339 Datasheet - Page 12

• Manufacturer Part Number: AD7339
• Description: 8-Bit I/O Port
• Manufacturer: Analog Devices

Specifications of AD7339

• Resolution (bits): 8bit
• # Chan: 1
• Sample Rate: 2MSPS
• Interface: Par
• Analog Input Type: SE-Uni
• Ain Range: 2 V p-p
• Adc Architecture: SAR
• Pkg Type: QFP

GROUNDING AND LAYOUT
The printed circuit board that houses the AD7339 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 separated. 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. If the AD7339 is the only device requiring an AGND-to-
DGND connection, the ground planes should be connected at
the AGND and DGND pins of the AD7339. If the AD7339 is
in a system where multiple devices require AGND-to-DGND
connections, the connection should be made at one point only,
AD7339. Avoid running digital lines under the device as these
will couple noise onto the die. The analog ground plane should
be allowed to run under the AD7339 to avoid noise coupling.
The power supply lines to the AD7339 should use as large a
track as possible to provide low impedance paths and reduce the
effects of glitches on the power supply line. Fast switching sig-
nals such as clocks should be shielded with digital ground to
avoid radiating noise to other sections of the board. Avoid
AD7339
a star point that should be established as close as possible to the
0.037 (0.95)
0.026 (0.65)
0.008 (0.20)
0.006 (0.15)
0.012 (0.30)
0.006 (0.15)
SEATING
PLANE
52-Lead Plastic Quad Flatpack (PQFP)
Dimensions shown in inches and (mm).
0.094 (2.39)
0.084 (2.13)
0.082 (2.09)
0.078 (1.97)
OUTLINE DIMENSIONS
13
1
(S-52)
52
14
–12–
0.0256
(0.65)
BSC
PIN 1
0.398 (10.11)
0.557 (14.15)
0.537 (13.65)
0.390 (9.91)
(PINS DOWN)
TOP VIEW
crossover of digital and analog signals. Traces at 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 dedicated to ground planes while signals are placed
on the other side. Good decoupling is important. The analog
and digital supplies to the AD7339 are independent and sepa-
rately pinned out to minimize coupling between analog and
digital sections of the device. All analog and digital supplies
should be decoupled to AGND and DGND respectively using
0.1 F ceramic capacitors in parallel with 10 F tantalum
capacitors. To achieve the best from the decoupling capaci-
tors, they should be placed as close as possible to the device,
ideally right up against the device. In systems where a com-
mon supply is used to drive both the AVDD and DVDD of
the AD7339, it is recommended that the system’s AVDD sup-
ply be used. This supply should have the recommended analog
supply decoupling between the AVDD pins of the AD7339 and
AGND and the recommended digital supply decoupling capaci-
tors between the DVDD pins and DGND.
0.014 (0.35)
0.010 (0.25)
40
26
39
27
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