Data Sheet

ADM3053

Rev. A | Page 15 of 20

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

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

of 100 nF and 10 μF as shown in Figure 28 (C5 and C8). Two

(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.

Figure 28. Recommended PCB Layout

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

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 AN-0971 Application Note, Control of Radiated Emissions

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.