Complete, Isolated, 3.3V

RS-485/RS-422 Data Interface

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13

__________Applications Information

The MAX3480A/MAX3480B are designed for bidirection-

al data communications on multipoint bus-transmission

lines. Figure 9 shows a typical network application cir-

cuit. To minimize reflections, terminate the line at both

ends with its characteristic impedance, and keep stub

lengths off the main line as short as possible. The slew-

rate-limited MAX3480B is more tolerant of imperfect ter-

mination and stubs off the main line.

The MAX3480A/MAX3480B are specified and charac-

terized using the resistor values shown in Table 1 of

Figure 2. Altering the recommended values can

degrade performance.

The DI and DE inputs are the cathodes of LEDs whose

driven by a 3.3V CMOS-logic gate with a series resis-

tor to limit the current. The resistor values shown in

Table 1 are recommended when the 74HC240 gate or

equivalent is used. These values may need to be

adjusted if a driving gate with dissimilar series resis-

tance is used. DI and DE are intended to be driven

through a series current-limiting resistor. Directly

grounding these pins destroys the device.