Datasheet

AD5040/AD5060
Rev. A | Page 20 of 24
USING THE AD5040/AD5060 WITH A
GALVANICALLY ISOLATED INTERFACE CHIP
In process control applications in industrial environments, it is
often necessary to use a galvanically isolated interface to protect
and isolate the controlling circuitry from any hazardous
common-mode voltages that can occur in the area where the
DAC is functioning. iCoupler® provides isolation in excess of
2.5 kV. Because the AD5040/AD5060 use a 3-wire serial logic
interface, the ADuM130x family provides an ideal digital
solution 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 2.7 V to 5.5 V, providing
compatibility with lower voltage systems as well as enabling a
voltage translation functionality across the isolation barrier.
Figure 52 shows a typical galvanically isolated configuration
using the AD5040/AD5060. The power supply to the part
also needs to be isolated; this is accomplished 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.
0.1μF10μF
V
DD
GND
POWER
5V
REGULATOR
04767-038
ADuM1300
SCLKV0AV1ASCLK
V
OUT
SYNCV0BV1BSDI
DINV0CV1CDATA
AD5040/
AD5060
Figure 52. AD5040/AD5060 with a Galvanically 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 are 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), as do 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 a 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 on 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.