ADR435 AD [Analog Devices], ADR435 Datasheet - Page 47

• Manufacturer Part Number: ADR435
• Description: Quad-Channel, 12-Bit, Serial Input, 4 mA to 20 mA Output
• Manufacturer: AD [Analog Devices]

Data Sheet
Traces
The power supply lines of the
as possible to provide low impedance paths and reduce the effects
of glitches on the power supply line. Fast switching signals such
as clocks should be shielded with digital ground to prevent radi-
ating noise to other parts of the board and should never be run
near the reference inputs. A ground line routed between the
SDIN and SCLK traces helps reduce crosstalk between them (not
required on a multilayer board that has a separate ground plane,
but separating the lines helps). It is essential to minimize noise on
the REFIN line because it couples through to the DAC output.
Avoid crossover of digital and analog signals. Traces on oppo-
site sides of the board should run at right angles to each other
to reduce the effects of feedthrough on the board. A microstrip
technique is by far the best method, but it is not always possible
with a double-sided board. In this technique, the component
side of the board is dedicated to ground plane, and signal traces
are placed on the solder side.
DC-to-DC Converters
To achieve high efficiency, good regulation, and stability, a
well-designed printed circuit board layout is required.
Follow these guidelines when designing printed circuit boards
(see Figure 77):
•
•
•
Keep the low ESR input capacitor, C
PGND.
Keep the high current path from C
(L
Keep the high current path from C
(L
(C
DCDC
DCDC
DCDC
) to SW
), the diode (D
) as short as possible.
x
and PGND as short as possible.
DCDC
AD5735
), and the output capacitor
should use as large a trace
IN
IN
IN
through the inductor
through the inductor
, close to AV
CC
and
Rev. B | Page 47 of 48
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•
•
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. The
Analog Devices iCoupler® products can provide voltage isolation
in excess of 2.5 kV. The serial loading structure of the
makes it ideal for isolated interfaces because the number of inter-
face lines is kept to a minimum. Figure 85 shows a 4-channel
isolated interface to the
more information, visit www.analog.com.
MICROCONTROLLER
Keep high current traces as short and as wide as possible.
The path from C
and PGND should be able to handle a minimum of 1 A.
Place the compensation components as close as possible to
the COMP
Avoid routing high impedance traces near any node
connected to SW
noise injection.
SERIAL CLOCK
CONTROL OUT
SERIAL DATA
Figure 85. 4-Channel Isolated Interface to the AD5735
SYNC OUT
OUT
OUT
DCDC_x
V
V
V
V
ADuM1411
IA
IB
IC
ID
IN
pin.
x
or near the inductor to prevent radiated
through the inductor (L
AD5735
ENCODE
ENCODE
ENCODE
ENCODE
using an ADuM1411. For
DECODE
DECODE
DECODE
DECODE
DCDC
V
V
V
V
OA
OB
OC
OD
) to SW
AD5735
TO SCLK
TO SDIN
TO SYNC
TO LDAC
AD5735
x