AD7680 Analog Devices, AD7680 Datasheet - Page 19

• Manufacturer Part Number: AD7680
• Manufacturer: Analog Devices

Specifications of AD7680

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 100kSPS
• Interface: Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni Vdd
• Adc Architecture: SAR
• Pkg Type: SOP,SOT

APPLICATION HINTS
GROUNDING AND LAYOUT
The printed circuit board that houses the AD7680 should be
designed 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. Digital and analog ground planes
should be joined at only one place. If the AD7680 is in a system
where multiple devices require an AGND to DGND
connection, the connection should still be made at one point
only, a star ground point that should be established as close as
possible to the AD7680.
Avoid running digital lines under the device because these
couple noise onto the die. The analog ground plane should be
allowed to run under the AD7680 to avoid noise coupling. The
power supply lines to the AD7680 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, such
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as clocks, should be shielded with digital ground to avoid
radiating noise to other sections of the board, and clock signals
should never be run near the analog inputs. Avoid crossover of
digital and analog signals. Traces on opposite sides of the board
should run at right angles to each other, which reduces the
effects of feedthrough on 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 the signals are placed on the
solder side.
Good decoupling is also very important. All analog supplies
should be decoupled with 10 μF tantalum in parallel with
0.1 μF capacitors to AGND, as discussed in the Typical
Connection Diagram section. To achieve the best performance
from these decoupling components, the user should attempt to
keep the distance between the decoupling capacitors and the
V
connecting the respective pins.
DD
and GND pins to a minimum, with short track lengths
AD7680