ADM3058E

Data Sheet

Rev. A | Page 16 of 18

APPLICATIONS INFORMATION

RADIATED EMISSIONS AND PCB LAYOUT

The ADM3058E isolated CAN transceivers with integrated

dc-to-dc converters pass EN 55022, Class B by 6 dB on a simple

2-layer PCB design. Neither stitching capacitance nor high

voltage surface-mount technology (SMT) safety capacitors are

required to meet this emission level.

PCB LAYOUT

The ADM3058E isolated CAN transceiver requires no external

interface circuitry for the logic interfaces. Power supply

The recommended bypass capacitor value is 0.1 μF. Note that

low effective series resistance (ESR) bypass capacitors are

required and must be placed as close to the chip pads as possible.

The total lead length between both ends of the capacitor and

the input power supply pin must not exceed 10 mm.

In applications involving high common-mode transients,

minimize board coupling across the isolation barrier. Design

the board layout so that any coupling that does occur equally

affects all pins on a given component side. Failure to ensure this

equal coupling can cause voltage differences between pins

exceeding the absolute maximum ratings of the device, thereby

leading to latch-up or permanent damage.

0.1µF

0.1µF

1

TXD

2

RXD

3

4

ADM3058E

Figure 22. Recommended PCB Layout

THERMAL ANALYSIS

The ADM3058E device consists of three internal die attached to a

split lead frame. For the purposes of thermal analysis, the die are

treated as a thermal unit, with the highest junction temperature

measurements taken with the devices mounted on a JEDEC

standard, 4-layer board with fine width traces and still air.

INSULATION LIFETIME

All insulation structures eventually break down when subjected

to voltage stress over a sufficiently long period of time. The rate

of insulation degradation is dependent on the characteristics of

the voltage waveform applied across the insulation as well as on

the materials and material interfaces.

The two types of insulation degradation of primary interest are

breakdown along surfaces exposed to air and insulation wear

out. Surface breakdown is the phenomenon of surface tracking

and is the primary determinant of surface creepage

requirements in system level standards. Insulation wear out

is the phenomenon where charge injection or displacement

currents inside the insulation material cause long-term

insulation degradation.

SURFACE TRACKING

Surface tracking is addressed in electrical safety standards by

setting a minimum surface creepage based on the working

voltage, the environmental conditions, and the properties of the

insulation material. Safety agencies perform characterization

testing on the surface insulation of components, allowing the

components to be categorized in different material groups.

Lower material group ratings are more resistant to surface

tracking and can therefore provide adequate lifetime with

smaller creepage. The minimum creepage for a given working

voltage and material group is in each system level standard and

is based on the total rms voltage across the isolation, pollution

degree, and material group.

The material group and creepage for the ADM3058E isolator is

listed in Table 3 for the 8-lead, wide body SOIC package.

INSULATION WEAR OUT

The lifetime of insulation caused by wear out is determined by

its thickness, material properties, and the voltage stress applied.

It is important to verify that the product lifetime is adequate at

the application working voltage. The working voltage supported by

an isolator for wear out may not be the same as the working

voltage supported for tracking. The working voltage applicable

to tracking is specified in most standards.

Testing and modeling have shown that the primary driver of

long-term degradation is displacement current in the polyimide

insulation causing incremental damage. The stress on the

insulation can be broken down into broad categories, such as

dc stress, which causes little wear out because there is no

displacement current, and an ac component time varying voltage

stress, which causes wear out.

The ratings in certification documents are usually based on

60 Hz sinusoidal stress because this reflects isolation from line

voltage. Many practical applications have combinations of 60 Hz

ac and dc across the barrier, as shown in Equation 1. Because

only the ac portion of the stress causes wear out, the equation

can be rearranged to solve for the ac rms voltage, as shown in

Equation 2. For insulation wear out with the polyimide materials

used in this product, the ac rms voltage determines the product

lifetime.

22

RMS

AC RMS

DC

VV

V



(1)

or

2

2

DC

RMS

RMS

AC

V

V

V





(2)

where: