Datasheet
MAX3480EA/MAX3480EB
±15kV ESD-Protected, Isolated, 3.3V
RS-485/RS-422 Data Interfaces
10 ______________________________________________________________________________________
The MAX3480EB features reduced-slew-rate drivers
that minimize EMI and reduce reflections caused by
improperly terminated cables, allowing error-free trans-
mission at data rates up to 160kbps. The MAX3480EA’s
driver slew rates are not limited, allowing transmission
rates up to 2.5Mbps.
The frequency-select FS is connected to GND_ in normal
operation, which selects a switching frequency of
approximately 600kHz. Connect to high for a higher
900kHz switching frequency.
Drivers are short-circuit current limited and are protect-
ed against excessive power dissipation by thermal
shutdown circuitry that puts the driver outputs into a
high-impedance state. The receiver input has a fail-safe
feature that guarantees a logic-high output if the input
is open circuit.
The driver outputs are enabled by bringing DE´ high.
Driver-enable times are typically 500ns for the
MAX3480EA and 1µs for the MAX3480EB. Allow time
for the devices to be enabled before sending data.
When enabled, driver outputs function as line drivers.
Driver outputs are high impedance when DE´ is low.
While outputs are high impedance, they function as line
receivers.
Figure 2. Typical Application Circuit
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
SHIELD (OPTIONAL)
EXTERNAL RS-485/RS-422 WIRING
ISO V
CC1
B
D2
D1
D1, D2
1N914
V
CC2
V
CC1
ISO RO DRV
A
B
A
SH
ISO DI IN
ISO DE IN
V
CC3
SD
FS
GND1
ISO COM1
ISO DI DRV
ISO V
CC2
ISO DE DRV
GND2
DE
V
CC4
DI
ISO COM2
ISO RO LED
V
CC5
RO
R
L
R
L
R4*
R5*
R1*
R2*
16
14
12
5
7
13
15
18
3
8 2
DI
DE
RO
17
20
9
10
11 RECEIVER OUTPUT
6
4
R8
100Ω
C3
0.01µF
C4
270pF
4kV
R6*
R7*
R3*
BOOSTED V+
74HC240
DRIVER INPUT
DRIVER ENABLE
V
IN
+3.0V TO +3.6V
C1
22µF
6V
C2
0.1µF
MAX3480EA/EB
LOGIC GROUND
ISOLATION BARRIER
1
2
28
27
3
4
5
6
7
8
9
10
11
12
13
14
26
25
24
23
22
21
20
19
18
17
16
15
ISOLATION COMMON
SHIELD (OPTIONAL)
NOTE: RESISTOR R8 PROTECTS
THE MAX3480E FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
A AND B.
TWISTED PAIR
TO OTHER TRANSCEIVERS
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
TWISTED PAIR
TO OTHER TRANSCEIVERS
MAX845
MAX1487E
MAX487E
*SEE TABLE 1.