ADM3065EARMZ-R7 datasheet(21/28 Pages) AD

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Data Sheet

ADM3061E/ADM3062E/ADM3063E/ADM3065E/ADM3066E/ADM3067E/ADM3068E

Rev. F | Page 21 of 28

THEORY OF OPERATION

IEC ESD PROTECTED RS-485

The 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. The ADM3061E/ADM3062E/

ADM3063E/ADM3065E/ADM3066E/ADM3067E/ADM3068E

can withstand up to ±12 kV contact discharge on transceiver

bus pins (A, B, Y, and Z) without latch-up or damage. The

ADM3061E/ADM3062E/ADM3063E has 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/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/

ADM3065E/ADM3066E/ADM3067E/ADM3068E driver output

differential 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 caused either 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.

tR = 0.7ns TO 1ns

IPEAK

I30ns

I60ns

30A

90%

16A

10%

30ns

60ns

TIME

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 subjected to three positive and three negative

discharges, whereas the IEC ESD standard requires 10 positive

and 10 negative discharge tests.

The ADM3061E/ADM3062E/ADM3063E/ADM3065E/

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

ratings is better suited for operation in harsh environments

compared to other RS-485 transceivers that state varying levels

of HBM ESD protection.

tR = 0.7ns TO 1ns

IPEAK

I30ns

I60ns

30A

90%

16A

5.33A

10%

30ns

10ns

60ns

TIME

IEC 61000-4-2 ESD 8kV

HBM ESD 8kV

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

Waveform 8 kV

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