Complete, Isolated RS-485/RS-422
Data Interface
V
CC3
ISO V
CC1
D1
D2
MAX845
Q
MAX1480A: MAX1487
MAX1480B: MAX487
MAX1480C: MAX487
N
OSC
1.07MHz/
1.45MHz
T
F/F
FS
B
A
ISO DI IN
D
Q
N
ISO DE IN
ISO RO DRV
R
GND1
RE
SD
ISO COM1
EXTERNAL RS-485/RS-422 WIRING
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
MAX1480A/B/C
V
V
V
5V
CC1
IN
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
TWISTED PAIR
TO OTHER TRANSCEIVERS
CC2
C1
22µF
C2
ISO V
CC1
R
R
L
3
D1
D2
B
0.1µF
B
4
SHIELD (OPTIONAL)
GND1
ISO RO DRV
A
5
A
TWISTED PAIR
TO OTHER TRANSCEIVERS
MAX1487
MAX487
MAX845
FS
6
SD
ISO DI IN
R6
SH
7
L
74HC86
OR EQUIVALENT
V
V
CC3
DI
ISO DE IN
8
R1
R4
SHIELD (OPTIONAL)
DI
DRIVER INPUT
ISO COM1
ISO DI DRV
9
DI´
CC4
DE
10
11
12
13
14
R2
R3
R5
NOTE: RESISTOR R7 PROTECTS
DE
DRIVER ENABLE
ISO V
CC2
THE MAX1480A/B/C FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
DE´
R7
100Ω
GND2
ISO DE DRV
ISO COM2
ISO RO LED
RECEIVER OUTPUT
RO
RO
V
CC5
LOGIC GROUND
ISOLATION BARRIER
ISOLATED COMMON
Table 1. Pull-Up and LED Drive Resistors
PART
R1 (Ω)
200
R2 (Ω)
200
R3 (Ω)
1000
3000
3000
R4 (Ω)
4300
2200
3000
R5 (Ω)
1000
3000
3000
R6 (Ω)
MAX1480A
MAX1480B
MAX1480C
200
200
200
200
510
200
200
Figure 1. MAX1480A/MAX1480B/MAX1480C Detailed Block Diagram and Typical Application Circuit
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B typically withstand 1600V (1 minute) or
Low-Power Shutdown Mode
The SD pin shuts down the oscillator on the internal power
driver. With the primary side in shutdown, no power is
transferred across the isolation barrier. The DI and DE
optocouplers, however, still consume current if the drive
signals on the nonisolated side are low. Therefore, leave
DI´ and DE´ high or floating when in shutdown mode.
RMS
2000V
(1 second). The logic inputs can be driven
RMS
from TTL/CMOS-logic with a series resistor, and the
received data output can directly drive TTL or CMOS-
logic families with only resistive pullup.
12 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
