Datasheet
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
10 ______________________________________________________________________________________
The high-speed optocouplers on the MAX1480EA/
MAX1480EC/MAX1490EA consume an additional 10mA
through V
CC5
(V
CC4
for the MAX1490EA). Therefore, to
completely shut down these devices, use an external P-
channel MOSFET as shown in Figure 3. In normal opera-
tion, SD is low, turning the MOSFET on and thereby
providing power to all the V
CC
pins. When SD is pulled
high, the power oscillator is disabled and the switch is
turned off, disconnecting power from the DI and DE opto-
couplers. In normal operating mode, the switch carries
only the optocoupler currents, so an on-resistance of sev-
eral ohms does not significantly degrade efficiency.
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
SHIELD (OPTIONAL)
EXTERNAL RS-485/RS-422 WIRING
ISO V
CC1
B
D2
D1
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*
R7
100Ω
R1*
R2*
R3*
R6*
DE
´
DI´
V
IN
+5V
C1
22µF
C2
0.1µF
LOGIC GROUND
ISOLATION BARRIER ISOLATED COMMON
DRIVER INPUT
DRIVER ENABLE
RECEIVER OUTPUT
DE
DI
RO
74HC86
OR EQUIVALENT
MAX1487E
MAX487E
MAX845E
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
MAX845E
N
MAX1480EA: MAX1487E
MAX1480EC: MAX487E
RE
ISO RO DRV
ISO DE IN
ISO DI IN
ISO COM1
ISO V
CC1
A
B
R
D
N
Q
Q
T F/F
V
CC3
FS
OSC
1.07MHz/
1.45MHz
SD
GND1
D2
D1
SHIELD (OPTIONAL)
NOTE: RESISTOR R7 PROTECTS
THE MAX1480EA FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
TWISTED PAIR
TO OTHER TRANSCEIVERS
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
TWISTED PAIR
TO OTHER TRANSCEIVERS
*SEE TABLE 1.
MAX1480EA
MAX1480EC
270pF
4kV
Figure 1. MAX1480EA/MAX1480EC Detailed Block Diagram and Application Circuit
Table 1. Pullup and LED Drive Resistors for Figure 1
PART R1 (Ω) R2 (Ω) R3 (Ω)
MAX1480EA
MAX1480EC
200
200
200
200
1000
3000
R4 (Ω)
4300
3000
R5 (Ω)
1000
3000
R6 (Ω)
200
200