9

FN6074.2

ESD Protection

All pins on these devices include class 3 Human Body

Model (HBM) ESD protection structures, but the RS-485

pins (driver outputs and receiver inputs) incorporate

advanced structures allowing them to survive ESD events

in excess of

±15kV HBM. The RS-485 pins are particularly

vulnerable to ESD damage because they typically connect

to an exposed port on the exterior of the finished product.

Simply touching the port pins, or connecting a cable, can

cause an ESD event that might destroy unprotected ICs.

These new ESD structures protect the device whether or

not it is powered up, protect without allowing any latchup

mechanism to activate, and without degrading the RS-485

common mode range of -7V to +12V. This built-in ESD

protection eliminates the need for board level protection

structures (e.g., transient suppression diodes), and the

associated, undesirable capacitive load they present.

FIGURE 6. DRIVER OUTPUT CURRENT vs DIFFERENTIAL

OUTPUT VOLTAGE

FIGURE 7. DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs

TEMPERATURE

FIGURE 8. DRIVER OUTPUT CURRENT vs SHORT CIRCUIT

VOLTAGE

FIGURE 9. SUPPLY CURRENT vs TEMPERATURE

DIFFERENTIAL OUTPUT VOLTAGE (V)

012

345

0

10

20

30

40

50

60

70

80

90

-40

0

50

85

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

TEMPERATURE (°C)

-25

25

75

OUTPUT VOLTAGE (V)

-7 -6

-4

-2

0

2

4

6

8

10

12

-60

-40

-20

0

20

40

60

80

100

120

140

160

-80

-100

-120

Y OR Z = HIGH

Y OR Z = LOW

ISL4491E

ISL4491E

ISL4489E

ISL4489E

-40

0

50

85

TEMPERATURE (°C)

-25

25

75

50

100

150

200

250

300

350

400

ISL4491E, DE = X, RE = X

ISL4489E, DE = X, RE = X

ISL4489E, ISL4491E