Complete, Isolated RS-485/RS-422

Data Interface

10

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________________________________________________________________Pin Description

Internal Connections. Leave these pins unconnected.

3, 4

3, 4

Logic-Side (nonisolated side) +5V Supply Voltages

1, 2, 8, 10

1, 2, 8, 10

FUNCTION

PIN

D1, D2

NAME

Shutdown Input. Ground for normal operation. When high, the power oscillator is

disabled.

7

7

= GND, switch frequency is low. For optimal performance and minimal supply

6

6

Logic-Side Ground. Connect to GND2 (pin 12).

5

5

SD

FS

GND1

Logic-Side (non-isolated side) +5V Supply Voltage

—

14

Receiver Output. If A > B by 200mV, RO will be low; if A < B by 200mV, RO will

—

13

Logic-Side Ground. Connect to GND1 (pin 5).

12

12

RO

GND2

Receiver Output. If A > B by 200mV, RO will be high; if A < B by 200mV, RO

11

—

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

´

high. The driver outputs are high impedance when DE

puts are enabled, the device functions as a line driver. While the driver outputs

are high impedance, the device functions as a line receiver. Drives internal

LED cathode through a resistor (Table 1 of Figure 1).

—

11

Driver Input. With DE

low and output B high. Similarly, a high on DI

B low. Drives internal LED cathode through a resistor (Table 1 of Figure 1 for

MAX1480A/B/C, Table 2 of Figure 2 for MAX1490A/B).

9

9

RO

DE

DI

Isolated Driver-Input Drive. With DE

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

high and output B low. Connect to ISO DI IN (on the MAX1480A/B/C only) for

(Table 1 of Figure 1 for MAX1480A/B/C; Table 2 of Figure 2 for MAX1490A/B).

15

19

pin 22 for MAX1490A/B).

14

18

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

ing DE

er 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-

for normal operation (Table 1 of Figure 1).

—

17

ISO DI DRV

ISO DE DRV

Isolated Common. Connect to ISO COM1 (pin 20).

—

16

Isolated Receiver Output LED. Internal LED anode in MAX1480A/B/C and LED

cathode in MAX1490A/B. Connect to ISO RO DRV through a resistor (Table 1 of

Figure 1 for MAX1480A/B/C; Table 2 of Figure 2 for MAX1490A/B).

13

15

Isolated Common. For MAX1480A/B/C, connect to ISO COM2 (pin 16)

(Figures 1 and 2).

16

20

ISO COM1

ISO COM2

ISO RO LED

MAX1480A/B/C

MAX1490A/B

PINS ON THE NON-ISOLATED SIDE

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

PINS ON THE NON-ISOLATED SIDE

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