
M
Complete, Isolated,
RS -485/RS -422 Data Interfac e
_______________________________________________________________________________________
9
_____________________________________________________________Pin Desc riptions
Internal Connections. Leave these pins unconnected.
Logic-Side Ground. Connect to GND2 (pin 12).
3, 4
5
3, 4
5
Logic-Side (non-isolated side) +5V Supply Voltages
1, 2, 8, 10
1, 2, 8, 10
FUNCTION
PIN
D1, D2
GND1
V
CC1
–V
CC4
NAME
Shutdown Input. Ground for normal operation. When high, the power oscillator is
disabled.
7
7
Frequency Switch Input. If FS = V
CC_
or is open, switch frequency is high; if FS
= 0V, switch frequency is low.
6
6
SD
FS
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
be high. Open collector; must have pull-up to V
CC_
(Table 1 of Figure 1).
—
13
Logic-Side Ground. Connect to GND1 (pin 5).
12
12
V
CC5
RO
GND2
Receiver Output. If A > B by 200mV, RO will be high; if A < B by 200mV, RO
will be low. Open collector; must have pull-up to V
CC
(Table 2 of Figure 2).
11
—
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).
—
11
Driver Input. With DE
′
high (MAX1480A/B 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
MAX1480, Table 2 of Figure 2 for MAX1490).
9
9
RO
DE
DI
Isolated Driver-Input Drive. With DE
′
high (MAX1480 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 MAX1480 only) for normal oper-
ation. Open-collector output; connect a pull-up resistor to ISO V
CC_
(Table 1 of
Figure 1 for MAX1480; Table 2 of Figure 2 for MAX1490).
Isolated Common. For MAX1480, connect to ISO COM2 (pin 16) (Figures 1 and 2).
15
19
Isolated Supply Voltage. Connect to ISO V
CC1
(pin 26 for MAX1480, or pin 22
for MAX1490).
14
18
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 pull-up to ISO VCC_ and be tied to ISO DE IN for
normal operation (Table 1 of Figure 1).
—
17
ISO DI DRV
ISO V
CC2
ISO DE DRV
Isolated Common. Connect to ISO COM1 (pin 20).
—
16
Isolated Receiver Output LED. Internal LED anode in MAX1480 and LED cath-
ode in MAX1490. Connect to ISO RO DRV through a resistor (Table 1 of Figure
1 for MAX1480; Table 2 of Figure 2 for MAX1490).
13
15
16
20
ISO COM1
ISO COM2
ISO RO LED
MAX1480A/B
MAX1490A/B
PINS ON THE NON-ISOLATED SIDE
PINS ON THE ISOLATED RS-485/RS-422 SIDE