ADM3053_12 AD [Analog Devices], ADM3053_12 Datasheet - Page 15

• Manufacturer Part Number: ADM3053_12
• Description: Signal and Power Isolated CAN Transceiver
• Manufacturer: AD [Analog Devices]

Data Sheet
APPLICATIONS INFORMATION
PCB LAYOUT
The ADM3053 signal and power isolated CAN transceiver
contains an isoPower integrated dc-to-dc converter, requiring
no external interface circuitry for the logic interfaces. Power
supply bypassing is required at the input and output supply pins
(see Figure 28). The power supply section of the ADM3053 uses
a 180 MHz oscillator frequency to pass power efficiently through
its chip-scale transformers. In addition, the normal operation of
the data section of the iCoupler introduces switching transients
on the power supply pins.
Bypass capacitors are required for several operating frequencies.
Noise suppression requires a low inductance, high frequency
capacitor, whereas ripple suppression and proper regulation
require a large value capacitor. These capacitors are connected
between GND1 and Pin 6 (V
a combination of 100 nF and 10 nF be placed as shown in Figure
28 (C6 and C4). It is recommended that a combination of two
capacitors, with values of 100 nF and 10 μF, are placed between
Pin 8 (V
and C1). The V
Pin 11 (GND2) and Pin 12 (V
of 100 nF and 10 μF as shown in Figure 28 (C5 and C8). Two
capacitors are recommended to be fitted Pin 19 (V
(GND2) with values of 100nF and 10nF as shown in Figure 28
(C9 and C7). The best practice recommended is to use a very low
inductance ceramic capacitor, or its equivalent, for the smaller
value. The total lead length between both ends of the capacitor
and the input power supply pin should not exceed 10 mm.
In applications involving high common-mode transients, ensure
that board coupling across the isolation barrier is minimized.
Furthermore, design the board layout such that any coupling
that does occur equally affects all pins on a given component
side. Failure to ensure this can cause voltage differentials between
CC
) and Pin 9 (GND1) for V
ISOIN
Figure 28. Recommended PCB Layout
and V
ISOOUT
IO
ISOOUT
) for V
capacitors are connected between
CC
) with recommended values
IO
as shown in Figure 28 (C2
. It is recommended that
ISOIN
) and Pin 20
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pins exceeding the absolute maximum ratings for the device,
thereby leading to latch-up and/or permanent damage.
The ADM3053 dissipates approximately 650 mW of power
when fully loaded. Because it is not possible to apply a heat sink
to an isolation device, the devices primarily depend on heat
dissipation into the PCB through the GND pins. If the devices
are used at high ambient temperatures, provide a thermal path
from the GND pins to the PCB ground plane. The board layout
in Figure 28 shows enlarged pads for Pin 1, Pin 3, Pin 9, Pin 10,
Pin 11, Pin 14, Pin 16, and Pin 20. Implement multiple vias from
the pad to the ground plane to reduce the temperature inside the
chip significantly. The dimensions of the expanded pads are at
the discretion of the designer and dependent on the available
board space.
EMI CONSIDERATIONS
The dc-to-dc converter section of the ADM3053 must, of
necessity, operate at very high frequency to allow efficient
power transfer through the small transformers. This creates
high frequency currents that can propagate in circuit board
ground and power planes, causing edge and dipole radiation.
Grounded enclosures are recommended for applications that
use these devices. If grounded enclosures are not possible, good
RF design practices should be followed in the layout of the PCB.
See the
with isoPower Devices, for more information.
INSULATION LIFETIME
All insulation structures eventually break down when subjected to
voltage stress over a sufficiently long period. The rate of insulation
degradation is dependent on the characteristics of the voltage
waveform applied across the insulation. Analog Devices conducts
an extensive set of evaluations to determine the lifetime of the
insulation structure within the ADM3053.
Accelerated life testing is performed using voltage levels higher
than the rated continuous working voltage. Acceleration factors for
several operating conditions are determined, allowing calculation
of the time to failure at the working voltage of interest. The values
shown in Table 5 summarize the peak voltages for 50 years of
service life in several operating conditions. In many cases, the
working voltage approved by agency testing is higher than the 50
year service life voltage. Operation at working voltages higher than
the service life voltage listed leads to premature insulation
failure.
The insulation lifetime of the ADM3053 depends on the voltage
waveform type imposed across the isolation barrier. The iCoupler
insulation structure degrades at different rates, depending on
whether the waveform is bipolar ac, unipolar ac, or dc. Figure 29,
Figure 30, and Figure 31 illustrate these different isolation voltage
waveforms.
AN-0971
Application Note, Control of Radiated Emissions
ADM3053