Datasheet

MAX3480A/MAX3480B
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
8 _______________________________________________________________________________________
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 V
CC
and be connected to ISO DE IN for
normal operation (Table 1 of Figure 2).
ISO DE
DRV
17
ISO RO
LED
15
Isolated-Supply Common Input. Connect to ISO COM1.ISO COM216
PIN FUNCTIONNAME
Isolated-Supply Positive Input Voltage. Connect to ISO V
CC1
.ISO V
CC2
18
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 V
CC
and be connected to ISO DI IN for normal operation (Table 1 of Figure 2).
ISO DI DRV19
Isolated-Supply Common Output. Connect to ISO COM2. If RS-485 wires have a shield, connect ISO
COM1 to shield via 100Ω resistor.
ISO COM120
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 IN21
Noninverting Driver Output and Noninverting Receiver Input.A23
Inverting Driver Output and Inverting Receiver InputB25
Isolated Driver Input. Connect to ISO DI DRV for normal operation.ISO DI IN22
Isolated Receiver-Output Drive. Connect to ISO RO LED through R6 (Table 1 of Figure 2).
ISO RO
DRV
24
Isolated Supply Positive Output Voltage. Connect to ISO V
CC2.
ISO V
CC1
26
Internal Connections. Leave these pins unconnected.AC2, AC127, 28
PINS ON THE ISOLATED RS-485/RS-422 SIDE