Complete, Isolated RS-485/RS-422
Data Interface
MAX1480A/B/C, MAX1490A/B
________________________________________________________________Pin Description
PIN
MAX1480A/B/C
MAX1490A/B
NAME
FUNCTION
PINS ON THE NON-ISOLATED SIDE
PINS ON THE NON-ISOLATED SIDE
1, 2, 8, 10
1, 2, 8, 10
V
CC1
–V
CC4
3, 4
3, 4
D1, D2
5
5
GND1
6
6
FS
Logic-Side (nonisolated side) +5V Supply Voltages
Internal Connections. Leave these pins unconnected.
Logic-Side Ground. Connect to GND2 (pin 12).
Frequency Select Input. If FS = V
CC_
or is open, switch frequency is high; if FS
= GND, switch frequency is low. For optimal performance and minimal supply
current, connect FS to V
CC_
or leave unconnected.
Shutdown Input. Ground for normal operation. When high, the power oscillator is
disabled.
Driver Input. With DE
´
high (MAX1480A/B/C only), 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. Drives internal LED cathode through a resistor (Table 1 of Figure 1 for
MAX1480A/B/C, Table 2 of Figure 2 for MAX1490A/B).
Driver-Enable 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 out-
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).
Receiver Output. If A > B by 200mV, RO will be high; if A < B by 200mV, RO
will be low. Open collector; must have pullup to V
CC
(Table 2 of Figure 2).
Logic-Side Ground. Connect to GND1 (pin 5).
Receiver Output.
If A > B by 200mV, RO will be low; if A < B by 200mV,
RO
will
be high. Open collector; must have pullup to V
CC_
(Table 1 of Figure 1).
Logic-Side (non-isolated side) +5V Supply Voltage
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).
Isolated Common. Connect to ISO COM1 (pin 20).
Isolated Driver-Enable Drive. The driver outputs, A and B, are enabled by bring-
ing DE
´
high. The driver outputs are high impedance when DE
´
is low. If the driv-
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-
collector output; must have pullup to ISO V
CC_
and be connected to ISO DE IN
for normal operation (Table 1 of Figure 1).
Isolated Supply Voltage. Connect to ISO V
CC1
(pin 26 for MAX1480A/B/C, or
pin 22 for MAX1490A/B).
Isolated Driver-Input Drive. With DE
´
high (MAX1480A/B/C only), 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. Connect to ISO DI IN (on the MAX1480A/B/C only) for
normal operation. Open-collector output; connect a pullup resistor to ISO V
CC_
(Table 1 of Figure 1 for MAX1480A/B/C; Table 2 of Figure 2 for MAX1490A/B).
Isolated Common. For MAX1480A/B/C, connect to ISO COM2 (pin 16)
(Figures 1 and 2).
7
7
SD
9
9
DI
11
—
DE
—
12
13
14
11
12
—
—
RO
GND2
RO
V
CC5
PINS ON THE ISOLATED RS-485/RS-422 SIDE
PINS ON THE ISOLATED RS-485/RS-422 SIDE
15
16
13
—
ISO RO LED
ISO COM2
17
—
ISO DE DRV
18
14
ISO V
CC2
19
15
ISO DI DRV
20
10
16
ISO COM1
______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
