AD7329 Analog Devices, AD7329 Datasheet - Page 37

• Manufacturer Part Number: AD7329
• Description: 1 MSPS , 8-Channel, Software Selectable True Bipolar Input, 12-Bit Plus Sign A/D Converter
• Manufacturer: Analog Devices

Specifications of AD7329

• Resolution (bits): 13bit
• # Chan: 8
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni,SE-Uni
• Ain Range: Bip (Vref),Bip (Vref) x 2,Bip (Vref) x 4,Bip 10V,Bip 2.5V,Bip 5.0V,Uni (Vref),Uni 10V
• Adc Architecture: SAR
• Pkg Type: SOP

APPLICATIONS INFORMATION
LAYOUT AND GROUNDING
The printed circuit board that houses the AD7329 should be
designed so that the analog and digital sections are confined to
certain areas of the board. This design facilitates the use of ground
planes that can be easily separated.
To provide optimum shielding for ground planes, a minimum
etch technique is generally best. All AGND pins on the AD7329
should be connected to the AGND plane. Digital and analog
ground pins should be joined in only one place. If the AD7329
is in a system where multiple devices require an AGND and
DGND connection, the connection should still be made at only
one point. A star point should be established as close as possible
to the ground pins on the AD7329.
Good connections should be made to the power and ground
planes. This can be done with a single via or multiple vias for
each supply and ground pin.
Avoid running digital lines under the AD7329 device because
this couples noise onto the die. However, the analog ground
plane should be allowed to run under the AD7329 to avoid
noise coupling. The power supply lines to the AD7329 device
should use as large a trace as possible to provide low impedance
paths and reduce the effects of glitches on the power supply line.
To avoid radiating noise to other sections of the board, com-
ponents, such as clocks, with fast switching signals should be
shielded with digital ground and never run near the analog inputs.
Avoid crossover of digital and analog signals. To reduce the effects
of feedthrough within the board, traces should be run at right
angles to each other. A microstrip technique is the best method,
but its use may not be possible with a double-sided board. In
this technique, the component side of the board is dedicated to
ground planes, and signals are placed on the other side.
Good decoupling is also important. All analog supplies should
be decoupled with 10 μF tantalum capacitors in parallel with
0.1 μF capacitors to AGND. To achieve the best results from
these decoupling components, they must be placed as close as
possible to the device, ideally right up against the device. The
0.1 μF capacitors should have a low effective series resistance
(ESR) and low effective series inductance (ESI), such as is typical
of common ceramic and surface-mount types of capacitors.
Rev. A | Page 37 of 40
These low ESR, low ESI capacitors provide a low impedance
path to ground at high frequencies to handle transient currents
due to internal logic switching.
POWER SUPPLY CONFIGURATION
If the supply voltage for the analog input circuitry is different
than that of the AD7329 V
may be applied to the AD7329 before V
is recommended that Schottky diodes be placed in series with the
AD7329 V
diode configuration. BAT43 Schottky diodes are used.
In an application where nonsymmetrical V
are used, adhere to the guidelines provided in Table 18, which
outlines the V
voltages when nonsymmetrical supplies are required. When
operating the AD7329 with low V
recommended that these supplies be symmetrical.
Table 18. Nonsymmetrical V
V
5 V
6 V
7 V
8 V
9 V
10 V to 16.5 V
For the 0 V to 4 × VREF range, V
the minimum supply recommendations outlined in Table 6.
DD
DD
and V
1
SS
ADDITIONAL PINS OMITTED FOR CLARITY.
supply range that can be used for various V
Figure 60. Schottky Diode Connection
SS
supply signals. Figure 60 shows the Schottky
V
V
IN
IN
0
7
DD
V
AD7329
V
V+
V–
Typical V
−5 V to −5.5 V
−5 V to −8.5 V
−5 V to −11.5 V
−5 V to −15 V
−5 V to −16.5 V
−5 V to −16.5 V
and V
DD
SS
DD
3V/5V
and V
V
SS
DD
SS
CC
1
can be tied to AGND as per
supplies or if the analog input
DOUT
SCLK
and V
SS
DIN
DD
CS
SS
Range
and V
Requirements
SS
DD
voltages, it is
and V
SS
are established, it
SS
AD7329
supplies
DD