MAX3480A Просмотр технического описания (PDF) - Maxim Integrated

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MAX3480A

Complete, Isolated, 3.3V RS-485/RS-422 Data Interface

Maxim Integrated 

Complete, Isolated, 3.3V

RS-485/RS-422 Data Interface

__________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

anodes are connected to VCC. These points are best

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.

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