AD5744R Analog Devices, AD5744R Datasheet - Page 29

• Manufacturer Part Number: AD5744R
• Description: Complete Quad, 14-Bit, High Accuracy, Serial Input, Bipolar Voltage Output D/A Converter
• Manufacturer: Analog Devices

Specifications of AD5744R

• Resolution (bits): 14bit
• Dac Update Rate: 1MSPS
• Dac Settling Time: 8µs
• Max Pos Supply (v): +16.5V
• Single-supply: No
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

Data Sheet
LAYOUT GUIDELINES
In any circuit where accuracy is important, careful considera-
tion of the power supply and ground return layout helps to ensure
the rated performance. Design the PCB on which the AD5744R
is mounted such that the analog and digital sections are separated
and confined to certain areas of the board. If the AD5744R is in
a system where multiple devices require an AGNDx-to-DGND
connection, establish the connection at one point only. Establish
the star ground point as close as possible to the device. The
AD5744R should have ample supply bypassing of 10 μF in parallel
with 0.1 μF on each supply located as close to the package as
possible, ideally right up against the device. The 10 μF capaci-
tors are of the tantalum bead type. The 0.1 μF capacitor should
have low effective series resistance (ESR) and low effective series
inductance (ESI), such as the common ceramic types that
provide a low impedance path to ground at high frequencies to
handle transient currents due to internal logic switching.
The power supply lines of the AD5744R should use as large a
trace as possible to provide low impedance paths and reduce
the effects of glitches on the power supply line. Shield fast-
switching signals, such as clocks with digital ground to avoid
radiating noise to other parts of the board; they should never be
run near the reference inputs. A ground line routed between
the SDIN and SCLK lines helps reduce cross-talk between them.
(A ground line is not required on a multi-layer board because
it has a separate ground plane; however, it is helpful to separate
the lines.) It is essential to minimize noise on the reference inputs
because it couples through to the DAC output. Avoid crossover
of digital and analog signals. Run traces on opposite sides of the
board at right angles to each other to reduce the effects of feed-
*ADDITIONAL PINS OMITTED FOR CLARITY.
MICROCONTROLLER
SERIAL CLOCK OUT
SERIAL DATA OUT
CONTROL OUT
SYNC OUT
V
V
V
V
IA
IB
IC
ID
ADuM1400*
Figure 44. Isolated Interface
Rev. E | Page 29 of 32
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through on the board. A microstrip technique is recommended
but not always possible with a double-sided board. In this
technique, the component side of the board is dedicated to the
ground plane, and the signal traces are placed on the solder side.
GALVANICALLY ISOLATED INTERFACE
In many process control applications, it is necessary to provide
an isolation barrier between the controller and the unit being
controlled to protect and isolate the controlling circuitry from
any hazardous common-mode voltages that may occur. Isocou-
plers provide voltage isolation in excess of 2.5 kV. The serial
loading structure of the AD5744R makes it ideal for isolated
interfaces because the number of interface lines is kept to a min-
imum. Figure 44 shows a 4-channel isolated interface to the
AD5744R using an
information on iCoupler products, refer to www.analog.com.
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD5744R is accomplished
using a serial bus that uses standard protocol that is compatible
with microcontrollers and DSP processors. The communications
channel is a 3-wire (minimum) interface consisting of a clock
signal, a data signal, and a synchronization signal. The AD5744R
requires a 24-bit data-word with data valid on the falling edge
of SCLK.
For all the interfaces, a DAC output update can be performed
automatically when all the data is clocked in, or it can be done
under the control of LDAC . The contents of the data register
can be read using the readback function.
DECODE
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DECODE
V
V
V
V
ADuM1400
OA
OB
OC
OD
TO SCLK
TO SDIN
TO SYNC
TO LDAC
iCoupler® product. For more
AD5744R