EVAL-AD5449EBZ Analog Devices Inc, EVAL-AD5449EBZ Datasheet - Page 24

• Manufacturer Part Number: EVAL-AD5449EBZ
• Description: BOARD EVALUATION FOR AD5449
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD5449EBZ

• Number Of Dac's: 2
• Number Of Bits: 12
• Outputs And Type: 2, Differential
• Sampling Rate (per Second): 2.47M
• Data Interface: Serial
• Settling Time: 80ns
• Dac Type: Current
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 125°C
• Utilized Ic / Part: AD5449
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5429/AD5439/AD5449
PCB LAYOUT AND POWER SUPPLY DECOUPLING
In any circuit where accuracy is important, careful considera-
tion of the power supply and ground return layout helps to
ensure the rated performance. The printed circuit board on
which the AD5429/AD5439/AD5449 is mounted should be
designed so that the analog and digital sections are separate
and confined to certain areas of the board. If the DAC is in a
system where 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.
The DAC should have ample supply bypassing of 10 μF in parallel
with 0.1 μF on the supply, located as close as possible to the
package, ideally right up against the device. The 0.1 μF capacitor
should have low effective series resistance (ESR) and low effective
series inductance (ESI), such as the common ceramic types of
capacitors 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.
Components, such as clocks, that produce fast-switching signals,
should be shielded with digital ground to avoid radiating noise
to other parts of the board, and they 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
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layout reduces the effects of feedthrough on the board. A micro-
strip technique is by far the best method, but its use is not always
possible with a double-sided board. In this technique, the compo-
nent side of the board is dedicated to the ground plane, and
signal traces are placed on the soldered side.
It is good practice to use 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 V
matched to minimize gain error. To maximize high frequency
performance, the I-to-V amplifier should be located as close as
possible to the device.
EVALUATION BOARD FOR THE DAC
The evaluation board consists of an AD5429/AD5439/AD5449
DAC and a current-to-voltage amplifier, the AD8065. Included
on the evaluation board is a 10 V reference, the 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.
Power Supplies for the Evaluation Board
The board requires ±12 V and +5 V supplies. The +12 V V
and −12 V V
supply is used to power the DAC (V
Both supplies are decoupled to their respective ground plane
with 10 μF tantalum and 0.1 μF ceramic capacitors.
SS
are used to power the output amplifier; the +5 V
REF
x and R
DD
) and transceivers (V
FB
x should also be
DD
CC
).