AD7949 Analog Devices, AD7949 Datasheet - Page 28

• Manufacturer Part Number: AD7949
• Description: 14-Bit, 8-Channel, 250 kSPS PulSAR ADC
• Manufacturer: Analog Devices

Specifications of AD7949

• Resolution (bits): 14bit
• # Chan: 8
• Sample Rate: 250kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni,SE-Uni
• Adc Architecture: SAR
• Pkg Type: CSP

AD7949
APPLICATION HINTS
LAYOUT
The printed circuit board (PCB) that houses the AD7949 should
be designed so that the analog and digital sections are separated
and confined to certain areas of the board. The pinout of the
AD7949, with all its analog signals on the left side and all 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 AD7949 is
used as a shield. Fast switching signals, such as CNV or clocks,
should not run near analog signal paths. Avoid crossover of
digital and analog signals.
At least one ground plane should be used. It can be common or
split between the digital and analog sections. In the latter case,
the planes should be joined underneath the AD7949.
The AD7949 voltage reference input REF has a dynamic input
impedance and should be decoupled with minimal parasitic
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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 power supplies VDD and VIO of the AD7949
should be decoupled with ceramic capacitors, typically 100 nF,
placed close to the AD7949, and connected using short, wide
traces to provide low impedance paths and to reduce the effect
of glitches on the power supply lines.
EVALUATING AD7949 PERFORMANCE
Other recommended layouts for the AD7949 are outlined in the
documentation of the evaluation board for the AD7949
AD7949EDZ). The evaluation board package includes a fully
assembled and tested evaluation board, documentation, and
software for controlling the board from a PC via the converter and
evaluation development data capture board, EVAL-CED1Z.
Data Sheet
(EVAL-