AD7690 Analog Devices, AD7690 Datasheet - Page 23

• Manufacturer Part Number: AD7690
• Manufacturer: Analog Devices

Specifications of AD7690

• Resolution (bits): 18bit
• # Chan: 1
• Sample Rate: 400kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: CSP,SOP

AD7690
APPLICATION HINTS
LAYOUT
The printed circuit board that houses the AD7690 should be
designed so that the analog and digital sections are separated
and confined to certain areas of the board. The pinout of the
AD7690, with its analog signals on the left side and its digital
signals on the right side, eases this task.
Avoid running digital lines under the device because these
couple noise onto the die unless a ground plane under the
AD7690 is used as a shield. Fast switching signals, such as CNV
or clocks, should not run near analog signal paths. Crossover of
digital and analog signals should be avoided.
At least one ground plane should be used. It can be common or
split between the digital and analog sections. In the latter case,
Figure 46. Example Layout of the AD7690 (Top Layer)
the planes should be joined underneath the AD7690s.
The AD7690 voltage reference input REF has a dynamic input
impedance and should be decoupled with minimal parasitic
inductances. This is done by placing the reference decoupling
ceramic capacitor close to, ideally right up against, the REF and
GND pins and connecting them with wide, low impedance traces.
Finally, the AD7690 VDD and VIO power supplies should be
decoupled with ceramic capacitors, typically 100 nF, placed
close to the AD7690 and connected using short, wide traces to
provide low impedance paths and to reduce the effect of glitches
on the power supply lines.
An example of a layout following these rules is shown in
Figure 46 and Figure 47.
EVALUATING THE AD7690’S PERFORMANCE
Figure 47. Example Layout of the AD7690 (Bottom Layer)
Other recommended layouts for the AD7690 are outlined
in the documentation of the evaluation board (EVAL-
AD7690CBZ). The evaluation board package includes
a fully assembled and tested evaluation board, documentation,
and software for controlling the board from a PC via the
EVAL-CONTROL BRD3.
Rev. B | Page 23 of 24