MAX3480ACPI datasheet(8/16 Pages) MAXIM

8 / 16 page

Complete, Isolated, 3.3V

RS-485/RS-422 Data Interface

_______________________________________________________________________________________

Note: For DE

´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit.

_________________________________________________Pin Description (continued)

Isolated Driver-Enable Drive Input. The driver outputs, A and B, are enabled by bringing DE

´ high.

The driver outputs are high impedance when DE

´ is low. If the driver outputs are enabled, the device

functions as a line driver. While the driver outputs are high impedance, the device functions as a line

receiver. Open collector output; must have pull-up (R4) to ISO VCC and be connected to ISO DE IN for

normal operation (Table 1 of Figure 2).

ISO DE

DRV

ISO RO

LED

Isolated-Supply Common Input. Connect to ISO COM1.

ISO COM2

FUNCTION

NAME

Isolated-Supply Positive Input Voltage. Connect to ISO VCC1.

ISO VCC2

Isolated Driver-Input Drive. With DE

´ high, a low on DI´ forces output A low and output B high. Similarly,

a high on DI

´ forces output A high and output B low. Open-collector output; must have pull-up (R5) to

ISO VCC and be connected to ISO DI IN for normal operation (Table 1 of Figure 2).

ISO DI DRV

Isolated-Supply Common Output. Connect to ISO COM2. If RS-485 wires have a shield, connect ISO

COM1 to shield via 100

Ω resistor.

ISO COM1

Isolated Receiver-Output LED Anode (input). If A > B by 200mV, ISO RO LED will be high; if A < B by

200mV, ISO RO LED will be low.

Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation.

ISO DE IN

Noninverting Driver Output and Noninverting Receiver Input.

Inverting Driver Output and Inverting Receiver Input

Isolated Driver Input. Connect to ISO DI DRV for normal operation.

ISO DI IN

Isolated Receiver-Output Drive. Connect to ISO RO LED through R6 (Table 1 of Figure 2).

ISO RO

DRV

Isolated Supply Positive Output Voltage. Connect to ISO VCC2.

ISO VCC1

Internal Connections. Leave these pins unconnected.

AC2, AC1

27, 28

PINS ON THE ISOLATED RS-485/RS-422 SIDE

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