AD5405 Analog Devices, AD5405 Datasheet - Page 19

• Manufacturer Part Number: AD5405
• Description: Dual 12-Bit, High Bandwidth, Multiplying DAC with 4 Quadrant Resistors and Parallel Interface
• Manufacturer: Analog Devices

Specifications of AD5405

• Resolution (bits): 12bit
• Dac Update Rate: 21.3MSPS
• Dac Settling Time: 80ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

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 AD5405 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 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), like 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 reduces the effects of feedthrough on the board. A
microstrip technique is by far the best, but its use is not always
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possible with a double-sided board. In this technique, the
component 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 DACS
The evaluation board consists of a DAC and a current-to-
voltage amplifier, the AD8065. Included on the evaluation
board is a 10 V reference, the ADR01. An external reference
may 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.
POWER SUPPLIES FOR THE EVALUATION BOARD
The board requires ±12 V and +5 V supplies. The +12 V V
and −12 V V
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
DD1
) and transceivers (V
REF
and R
FB
should also be
AD5405
CC
).
DD