EVAL-AD5425EBZ Analog Devices Inc, EVAL-AD5425EBZ Datasheet - Page 22

• Manufacturer Part Number: EVAL-AD5425EBZ
• Description: BOARD EVALUATION FOR AD5425
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD5425EBZ

• Number Of Dac's: 1
• Number Of Bits: 8
• Outputs And Type: 1, Differential
• Sampling Rate (per Second): 2.47M
• Data Interface: Serial
• Settling Time: 15ns
• Dac Type: Current
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 125°C
• Utilized Ic / Part: AD5425
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5425
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 AD5425 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 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.
These DACs should have an ample supply bypassing of 10 μF in
parallel with 0.1 μF on the supply and located as close to the
package as possible—ideally up against the device. The 0.1 μF
capacitor should have low effective series resistance (ESR) and
effective series inductance (ESI), such as found in 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 to 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 through 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 ground plane while
signal traces are placed on the solder side.
Rev. A | Page 22 of 28
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 V
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.
EVALUATION BOARD
The board consists of an 8-bit AD5425 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 simply allows the
user to write a code to the device.
OPERATING THE EVALUATION BOARD
Power Supplies
The board requires ±12 V and 5 V supplies. The 12 V V
V
to power the DAC (V
Both supplies are decoupled to their respective ground plane
with 10 μF tantalum and 0.1 μF ceramic capacitors.
Link1 (LK1) is provided to allow selection between the on-
board reference (ADR01) or an external reference applied
through J2. Link2 should be connected to the LDAC position.
SS
are used to power the output amplifier, while the 5 V is used
DD1
) and transceivers (V
REF
and R
FB
should also be
CC
).
DD
and