Complete, Isolated RS-485/RS-422
Data Interface
MAX1480A/B/C, MAX1490A/B
V
CC3
ISO V
CC1
MAX845
Q
FS
OSC
1.07MHz/
1.45MHz
T F/F
D2
Q
N
ISO DE IN
ISO RO DRV
SD
GND1
RE
R
N
ISO DI IN
D
A
D1
MAX1480A: MAX1487
MAX1480B: MAX487
MAX1480C: MAX487
B
ISO COM1
EXTERNAL RS-485/RS-422 WIRING
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
28 AC1 (MAKE NO CONNECTION)
27 AC2 (MAKE NO CONNECTION)
26 ISO V
CC1
B
25
24
MAX845
MAX1487
MAX487
ISO RO DRV
A
R6
R4
SH
B
SHIELD (OPTIONAL)
TWISTED PAIR
TO OTHER TRANSCEIVERS
R
L
SHIELD (OPTIONAL)
TWISTED PAIR
TO OTHER TRANSCEIVERS
R
L
V
IN
5V
C1
22µF
C2
0.1µF
V
CC1
V
CC2
MAX1480A/B/C
1
2
D1 3
D2 4
GND1
5
FS 6
SD
7
V
CC3
R1
DI
V
CC4
DE
GND2
8
9
10
11
12
23 A
22 ISO DI IN
21
ISO DE IN
74HC86
OR EQUIVALENT
DI
DRIVER INPUT
DI
´
DE
DRIVER ENABLE
DE
´
RECEIVER OUTPUT
RO
R2
R3
20 ISO COM1
19 ISO DI DRV
18 ISO V
CC2
17 ISO DE DRV
16
15
ISOLATION BARRIER
ISO COM2
ISO RO LED
R5
R7
100Ω
NOTE: RESISTOR R7 PROTECTS
THE MAX1480A/B/C FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
RO 13
V
CC5
14
LOGIC GROUND
ISOLATED COMMON
Table 1. Pull-Up and LED Drive Resistors
PART
MAX1480A
MAX1480B
MAX1480C
R1 (Ω)
200
200
200
R2 (Ω)
200
510
200
R3 (Ω)
1000
3000
3000
R4 (Ω)
4300
2200
3000
R5 (Ω)
1000
3000
3000
R6 (Ω)
200
200
200
Figure 1. MAX1480A/MAX1480B/MAX1480C Detailed Block Diagram and Typical Application Circuit
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B typically withstand 1600V
RMS
(1 minute) or
2000V
RMS
(1 second). The logic inputs can be driven
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.
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.
12
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
