AD5762R Analog Devices, AD5762R Datasheet - Page 30

• Manufacturer Part Number: AD5762R
• Description: Complete Dual, 16-Bit, High Accuracy, Serial Input, Bipolar Voltage Output DAC
• Manufacturer: Analog Devices

Specifications of AD5762R

• Resolution (bits): 16bit
• Dac Update Rate: 84.6kSPS
• Dac Settling Time: 8µs
• Max Pos Supply (v): +16.5V
• Single-supply: No
• Dac Type: Voltage Out
• Dac Input Format: Ser,SPI

AD5762R
LAYOUT GUIDELINES
In any circuit where accuracy is important, careful consideration
of the power supply and ground return layout helps to ensure the
rated performance. Design the PCB on which the AD5762R is
mounted such that the analog and digital sections are separated
and confined to certain areas of the board. If the AD5762R 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
AD5762R should have ample supply bypassing of 10 μF in parallel
with 0.1 μF on each supply located as close to the package as pos-
sible, ideally right up against the device. The 10 μF capacitors
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 AD5762R 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 refer-
ence 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 multilayer 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
*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. C | Page 30 of 32
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to each other to reduce the effects of feedthrough 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 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.
Isocouplers provide voltage isolation in excess of 2.5 kV. The
serial loading structure of the AD5762R makes it ideal for
isolated interfaces because the number of interface lines is kept
to a minimum. Figure 44 shows a 4-channel isolated interface
to the AD5762R using an
more information on iCoupler products, go to www.analog.com.
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD5762R is accomplished
using a serial bus that uses standard protocol that is compatible
with microcontrollers and DSP processors. The communication
channel is a 3-wire (minimum) interface consisting of a clock
signal, a data signal, and a synchronization signal. The AD5762R
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 DAC register
can be read using the readback function.
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V
V
V
V
OA
OB
OC
OD
ADuM1400
TO SCLK
TO SDIN
TO SYNC
TO LDAC
iCoupler® product. For
Data Sheet