EVAL-AD5429EB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
EVAL-AD5429EB
Analog Devices
'EVAL-AD5429EB' PDF : 32 Pages View PDF
AD5429/AD5439/AD5449
PCB LAYOUT AND POWER SUPPLY DECOUPLING
In any circuit where accuracy is important, careful consider-
ation of the power supply and ground return layout helps to
ensure the rated performance. The printed circuit board on
which the DAC is mounted should be designed so that the
analog and digital sections are separated and confined to
certain areas of the board. If the DAC is in a system in which
multiple devices require an AGND to DGND connection, the
connection should be made at one point only. The star ground
point should be established as close as possible to the device.
These DACs should have ample supply bypassing of 10 µF
in parallel with 0.1 µF on the supply located as close to the
package as possible, ideally right up against the device. The
0.1 µF capacitor should have low effective series resistance
(ESR) and effective series inductance (ESI), like the common
ceramic types that provide a low impedance path to ground at
high frequencies, to handle transient currents due to internal
logic switching. Low ESR 1 µF to 10 µF tantalum or electrolytic
capacitors should also be applied at the supplies to minimize
transient disturbance and filter out low frequency ripple.
Fast switching signals such as clocks should be shielded with
digital ground to avoid radiating noise to other parts of the
board, and should never be run near the reference inputs.
Avoid crossover of digital and analog signals. Traces on opposite
sides of the board should run at right angles to each other. This
reduces the effects of feedthrough on the board. A microstrip
technique is by far the best, but not always possible with a
double-sided board. In this technique, the component side of
the board is dedicated to the ground plane, while signal traces
are placed on the soldered side.
It is good practice to employ compact, minimum lead-length
PCB layout design. Leads to the input should be as short as
possible to minimize IR drops and stray inductance.
The PCB metal traces between VREF and RFB should also be
matched to minimize gain error. To maximize high frequency
performance, the I-to-V amplifier should be located as close to
the device as possible.
POWER SUPPLIES FOR THE EVALUATION BOARD
The board requires ±12 V and +5 V supplies. The 12 V VDD
and VSS are used to power the output amplifier, while the 5 V
is used to power the DAC (VDD1) and transceivers (VCC).
Both supplies are decoupled to their respective ground plane
with 10 µF tantalum and 0.1 µF ceramic capacitors.
EVALUATION BOARD FOR THE DACS
The evaluation board includes a DAC from the AD5429/
AD5439/AD5449 family and a current-to-voltage amplifier,
AD8065. On the evaluation board is a 10 V reference, ADR01.
An external reference can also be applied via an SMB input.
The evaluation kit consists of a CD-ROM with self-installing
PC software to control the DAC. The software allows the user to
write a code to the device.
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