Data Sheet

ADM3061E/ADM3062E/ADM3063E/ADM3064E/

ADM3065E/ADM3066E/ADM3067E/ADM3068E

THEORY OF OPERATION

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Rev. H | 18 of 25

IEC ESD PROTECTED RS-485

The ADM3061E/ADM3062E/ADM3063E/ADM3064E/ADM3065E/

ADM3066E/ADM3067E/ADM3068E are 3.0 V to 5.5 V, 50 Mbps

RS-485 transceivers with IEC 61000-4-2 Level 4 ESD protection

on the bus pins. These devices can withstand up to ±12 kV

contact discharge on transceiver bus pins (A, B, Y, and Z) with-

out latch-up or damage. The ADM3061E/ADM3062E/ADM3063E/

ADM3064E have the same robust IEC 61000-4-2 ESD protection

as the ADM3065E/ADM3066E/ADM3067E/ADM3068E models, and

operate at a lower, 500 kbps data rate.

HIGH DRIVER DIFFERENTIAL OUTPUT

VOLTAGE

The ADM3061E/ADM3062E/ADM3063E/ADM3064E/ADM3065E/

ADM3066E/ADM3067E/ADM3068E have characteristics that are

optimized for use in PROFIBUS applications. When powered at

VCC ≥ 4.5 V, the ADM3061E/ADM3062E/ADM3063E/ADM3064E/

ADM3065E/ADM3066E/ADM3067E/ADM3068E driver output differ-

ential voltage meets or exceeds the PROFIBUS requirements of 2.1

V with a 54 Ω load.

IEC 61000-4-2 ESD PROTECTION

ESD is the sudden transfer of electrostatic charge between bodies

at different potentials either caused by near contact or induced by

an electric field. It has the characteristics of high current in a short

time period. The primary purpose of the IEC 61000-4-2 test is to

determine the immunity of systems to external ESD events outside

the system during operation. IEC 61000-4-2 describes testing using

two coupling methods: contact discharge and air discharge. Contact

discharge implies a direct contact between the discharge gun and

the equipment under test (EUT). During air discharge testing, the

charged electrode of the discharge gun is moved toward the EUT

until a discharge occurs as an arc across the air gap. The discharge

gun does not make direct contact with the EUT. A number of

factors affect the results and repeatability of the air discharge test,

including humidity, temperature, barometric pressure, distance, and

rate of approach to the EUT. This method is a more accurate

representation of an actual ESD event but is not as repeatable.

Therefore, contact discharge is the preferred test method.

During testing, the data port is subjected to at least 10 positive

and 10 negative single discharges. Selection of the test voltage is

dependent on the system end environment.

Figure 45 shows the 8 kV contact discharge current waveform as

described in the IEC 61000-4-2 specification. Some of the key

waveform parameters are rise times of less than 1 ns and pulse

widths of approximately 60 ns.

Figure 45. IEC 61000-4-2 ESD Waveform (8 kV)

Figure 46 shows the 8 kV contact discharge current waveform

from the IEC 61000-4-2 standard compared to the HBM ESD

8 kV waveform. Figure 46 shows that the two standards specify

a different waveform shape and peak current. The peak current

associated with an IEC 61000-4-2 8 kV pulse is 30 A, whereas

the corresponding peak current for HBM ESD is more than five

times less at 5.33 A. The other difference is the rise time of the

initial voltage spike, with the IEC 61000-4-2 ESD waveform having

a much faster rise time of 1 ns, compared to the 10 ns associated

with the HBM ESD waveform. The amount of power associated with

an IEC ESD waveform is much greater than that of an HBM ESD

waveform. The HBM ESD standard requires the EUT to be subject-

ed to three positive and three negative discharges, whereas the

IEC ESD standard requires 10 positive and 10 negative discharge

tests.

The ADM3061E/ADM3062E/ADM3063E/ADM3064E/ADM3065E/

ADM3066E/ADM3067E/ADM3068E with IEC 61000-4-2 ESD rat-

ings is better suited for operation in harsh environments compared

to other RS-485 transceivers that state varying levels of HBM ESD

protection.

Figure 46. IEC 61000-4-2 ESD Waveform (8 kV) Compared to HBM ESD

Waveform (8 kV)

TRUTH TABLES

Table 13 and Table 14 use the abbreviations shown in Table 12.