AD7476AYRM Analog Devices Inc, AD7476AYRM Datasheet - Page 25

• Manufacturer Part Number: AD7476AYRM
• Description: IC ADC 12BIT 2.35V 1MSPS 8-MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD7476AYRM

• Rohs Status: RoHS non-compliant
• Design Resources: Output Channel Monitoring Using AD5380 (CN0008) AD5382 Channel Monitor Function (CN0012) AD5381 Channel Monitor Function (CN0013) AD5383 Channel Monitor Function (CN0015) AD5390/91/92 Channel Monitor Function (CN0030) Power off protected data acquisition signal chain using ADG4612 , AD711, and AD7476 (CN0165)
• Number Of Bits: 12
• Sampling Rate (per Second): 1M
• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 17.5mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• For Use With: EVAL-AD7476ACBZ - BOARD EVALUATION FOR AD7476AAD7476-DBRD - BOARD EVAL FOR AD7476AD7476A-DBRD - BOARD EVAL FOR AD7476A

APPLICATION HINTS
GROUNDING AND LAYOUT
Design the printed circuit board that houses the AD7476A/
AD7477A/AD7478A such 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 separated easily.
A minimum etch technique is generally best for ground planes
because it gives the best shielding. Join digital and analog
ground planes at only one place. If the AD7476A/AD7477A/
AD7478A is in a system where multiple devices require an
AGND to DGND connection, make the connection at one
point only, a star ground point that is established as close as
possible to the AD7476A/AD7477A/AD7478A.
Avoid running digital lines under the device as these couple
noise onto the die. Allow the analog ground plane to run under
the AD7476A/AD7477A/AD7478A in order to avoid noise
coupling. Use as large a trace as possible on the power supply
lines to the AD7476A/AD7477A/AD7478A to provide low
impedance paths and reduce the effects of glitches on the power
supply line. Shield fast switching signals like clocks with digital
grounds to avoid radiating noise to other sections of the board,
and never run clock signals near the analog inputs. Avoid crossover
of digital and analog signals. Run traces on opposite sides of the
board at right angles to each other. This reduces 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 solder side.
Good decoupling is also very important. Decouple the supply
with, for instance, a 680 nF 0805 capacitor to GND. When using
the SC70 package in applications where the size of the components
is of concern, a 220 nF 0603 capacitor, for example, can be used
instead. However, in that case, the decoupling may not be as
effective, resulting in an approximate SINAD degradation of
0.3 dB. To achieve the best performance from these decoupling
components, the user should endeavor to keep the distance
between the decoupling capacitor and the V
a minimum with short track lengths connecting the respective
pins. Figure 31 and Figure 32 and show the recommended
positions of the decoupling capacitor for the SC70 and MSOP
packages, respectively.
Figure 31. Recommended Supply Decoupling Scheme for the SC70 Package
DD
and GND pins to
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As can be seen in Figure 32, for the MSOP package, the
decoupling capacitor has been placed as close as possible to the
IC with short track lengths to V
decoupling capacitor can also be placed on the underside of the
PCB directly underneath the IC, between the V
pins attached by vias. This method is not recommended on
PCBs above a standard 1.6 mm thickness. The best performance
is realized with the decoupling capacitor on the top of the PCB
next to the IC.
Similarly, for the SC70 package, locate the decoupling capacitor
as close as possible to the V
pinout, that is, V
can be placed extremely close to the IC. The decoupling capacitor
can be placed on the underside of the PCB directly under the
V
the decoupling capacitor on the same side as the IC.
EVALUATING THE AD7476A/AD7477A
PERFORMANCE
The evaluation board package includes a fully assembled and
tested evaluation board, documentation, and software for
controlling the board from the PC via the EVAL-BOARD
CONTROLLER. The EVAL-BOARD CONTROLLER can be
used in conjunction with the AD7476ACB/AD7477ACB
evaluation board, as well as many other Analog Devices
evaluation boards ending in the CB designator, to
demonstrate/evaluate the ac and dc performance of the
AD7476A/AD7477A. The software allows the user to perform
ac (fast Fourier transform) and dc (histogram of codes) tests on
the AD7476A/AD7477A. See the evaluation board application
note for more information.
DD
and GND pins, but the best performance is achieved with
Figure 32. Recommended Supply Decoupling Scheme for the
AD7476A/AD7477A/AD7478A MSOP Package
DD
AD7476A/AD7477A/AD7478A
being next to GND, the decoupling capacitor
DD
and the GND pins. Because of its
DD
and GND pins. The
DD
and GND