AD5735 Analog Devices, AD5735 Datasheet - Page 46

• Manufacturer Part Number: AD5735
• Description: Quad Channel, 12-Bit, Serial Input, 4-20 mA & Voltage Output DAC with Dynamic Power Control
• Manufacturer: Analog Devices

Specifications of AD5735

• Resolution (bits): 12bit
• Dac Settling Time: 11µs
• Max Pos Supply (v): +33V
• Single-supply: No
• Dac Type: I or V Out
• Dac Input Format: SPI

AD5735
DRIVING INDUCTIVE LOADS
When driving inductive or poorly defined loads, a capacitor
may be required between the I
ensure stability. A 0.01 μF capacitor between I
ensures stability of a load of 50 mH. The capacitive component
of the load may cause slower settling, although this may be
masked by the settling time of the AD5735. There is no maxi-
mum capacitance limit for the current output of the AD5735.
TRANSIENT VOLTAGE PROTECTION
The
age from normal handling. The industrial control environment
can, however, subject I/O circuits to much higher transients. To
protect the
external power diodes and a surge current limiting resistor (R
are required, as shown in Figure 83. A typical value for R
The two protection diodes and the resistor (R
priate power ratings.
Further protection can be provided using transient voltage
suppressors (TVSs), also referred to as transorbs. These compo-
nents are available as unidirectional suppressors, which protect
against positive high voltage transients, and as bidirectional
suppressors, which protect against both positive and negative
high voltage transients. Transient voltage suppressors are avail-
able in a wide range of standoff and breakdown voltage ratings.
The TVS should be sized with the lowest breakdown voltage
possible while not conducting in the functional range of the
current output.
It is recommended that all field connected nodes be protected.
The voltage output node can be protected with a similar circuit,
where D2 and the transorb are connected to AV
age output node, the +V
a large value series resistance to the transorb, such as 5 kΩ. In
this way, the I
share the same protection circuitry.
CONVERTER)
DC-TO-DC
AD5735
(FROM
C
4.7µF
DCDC
AD5735
Figure 83. Output Transient Voltage Protection
contains ESD protection diodes that prevent dam-
OUT_x
R
FILTER
10Ω
and V
from excessively high voltage transients,
SENSE_x
OUT_x
C
0.1µF
FILTER
AD5735
V
pins can also be tied together and
BOOST_x
OUT_x
pin should also be protected with
AGND
I
OUT_x
pin and the AGND pin to
D1
D2
R
P
P
) must have appro-
OUT_x
SS
. For the volt-
and AGND
R
P
LOAD
is 10 Ω.
Rev. A | Page 46 of 48
P
)
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the
that uses a protocol 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 latch
signal. The
on the falling edge of SCLK.
The DAC output update is initiated either on the rising edge of
LDAC or, if LDAC is held low, on the rising edge of SYNC . The
contents of the registers can be read using the readback function.
AD5735-to-ADSP-BF527 Interface
The
of the ADSP-BF527, an Analog Devices, Inc., Blackfin® DSP.
Figure 84 shows how the SPORT interface can be connected
to control the AD5735.
LAYOUT GUIDELINES
Grounding
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
analog and digital sections are separated and confined to
certain areas of the board. If the
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.
The GNDSW
supply are referred to as PGND. PGND should be confined to
certain areas of the board, and the PGND-to-AGND connection
should be made at one point only.
Supply Decoupling
The
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 capac-
itors are the tantalum bead type. The 0.1 μF capacitors should
have low effective series resistance (ESR) and low effective series
inductance (ESL), such as the common ceramic types, which
provide a low impedance path to ground at high frequencies to
handle transient currents due to internal logic switching.
AD5735
AD5735
ADSP-BF527
AD5735
Figure 84. AD5735-to-ADSP-BF527 SPORT Interface
AD5735
SPORT_TSCLK
can be connected directly to the SPORT interface
should have ample supply bypassing of 10 μF in
x
pin and the ground connection for the AV
SPORT_TFS
SPORT_DT0
is mounted should be designed so that the
GPIO0
requires a 24-bit data-word with data valid
AD5735
AD5735
SYNC
SCLK
SDIN
LDAC
is in a system where
is via a serial bus
AD5735
Data Sheet
CC