
AD5040/5060
Preliminary Technical Data
Rev. PrC | Page 16 of 17
where
D
represents the input code in decimal (0–65535).
With
VDD
= 5 V,
R
1 =
R
2 = 10 kW:
This is an output voltage range of ±5 V with 0000Hex
corresponding to a –5 V output and 3FFF Hex
corresponding to a +5 V output.
Figure 30. Bipolar Operation with the AD5040/AD5060
Using AD5040/AD5060 with an Opto-Isolated
Interface
In process-control applications in industrial environments it is
often necessary to use an opto-isolated interface to protect and
isolate the controlling circuitry from any hazardous common-
mode voltages that may occur in the area where the DAC is
functioning. Because the AD5040/AD5060 uses a three-wire
serial logic interface, the ADuM130Xifamily s an ideal way to
provide digital isolation for the DAC interface.
The ADuM130x isolators provide three independent isolation
channels in a variety of channel configurations and data rates.
They operate across the full range from 2.7V to 5.5V, providing
compatibility with lower voltage systems as well as enabling a
voltage translation functionality across the isolation barrier.
Figure 31. The power supply to the part also needs to be
isolated. This is done by using a transformer. On the DAC side
of the transformer, a +5 V regulator provides the +5 V supply
required for the AD5040/AD5060.
0.1
.
F
+5V
REGULATOR
V
OUT
GND
DIN
SCLK
POWER
10
.
F
V
DD
SCLK
DATA
DAC
SDI
ADMu103x
SDI
V1A
V1B
V1C
VOA
VOB
VOC
Figure 31. AD5040/AD5060 with An Opto-Isolated Interface
Power Supply Bypassing and Grounding
When accuracy is important in a circuit it is helpful to carefully
consider the power supply and ground return layout on the
board. The printed circuit board containing the
AD5040/AD5060 should have separate analog and digital
sections, each having its own area of the board. If the
AD5040/AD5060 is in a system where other devices require an
AGND to DGND connection, the connection should be
made at one point only. This ground point should be
as close as possible to the AD5040/AD5060.
The power supply to the AD5040/AD5060 should be
bypassed with
10 μF and 0.1 μF capacitors. The capacitors should be
physically as close as possible to the device with the 0.1 μF
capacitor ideally right up against the device. The 10 μF
capacitors are the tantalum bead type. It is important that the
0.1 μF capacitor has low Effective Series Resistance (ESR) and
Effective Series Inductance (ESI), e.g., common ceramic types
of capacitors. This 0.1 μF capacitor provides a low impedance
path to ground for high frequencies caused by transient
currents due to internal logic switching.
The power supply line itself should have as large a trace as
possible to provide a low impedance path and reduce glitch
effects on the supply line. Clocks and other fast switching
digital signals should be shielded from other parts of
the board by digital ground. Avoid crossover of digital and
analog signals if possible. When traces cross on opposite sides
of the board, ensure that they run at right angles to each other
to reduce feedthrough effects through the board. The best
board layout technique is the microstrip technique where the
component side of the board is dedicated to the ground plane
only and the signal traces are placed on the solder side.
However, this is not always possible with a two-layer board.