MAX1480A_05 Datasheet, PDF (12/21 Pages) Maxim Integrated Products – Complete, Isolated RS-485/RS-422 Data Interface

Complete, Isolated RS-485/RS-422
Data Interface
V_CC3
Q
FS
OSC
1.07MHz/
T F/F
1.45MHz
Q
MAX845
D1
N
D2
N
SD
GND1
ISO DI IN
ISO DE IN
ISO RO DRV
ISO V_CC1
MAX1480A: MAX1487
MAX1480B: MAX487
MAX1480C: MAX487
B
D
A
R
RE
V_IN
5V
C1
22µF
C2
0.1µF
74HC86
OR EQUIVALENT
DI
DRIVER INPUT
R1
DI´
R2
DE
DRIVER ENABLE
DE´
R3
RECEIVER OUTPUT
RO
ISO COM1
V_{CC1 1}
V_{CC2 2}
D1 3
D2 4
GND1 ₅
FS 6
SD ₇
V_{CC3 8}
DI ₉
V_{CC4 10}
DE ₁₁
GND2 ₁₂
RO ₁₃
V_{CC5 14}
MAX1480A/B/C
MAX845
MAX1487
MAX487
28 AC1 (MAKE NO CONNECTION)
27 AC2 (MAKE NO CONNECTION)
26 ^{ISO VCC1}
B
25
24 ^{ISO RO DRV}
23 ^A
22 ^{ISO DI IN}
R6
21 ^{ISO DE IN}
20 ^{ISO COM1}
R4
19 ^{ISO DI DRV}
18 ^{ISO VCC2}
R5
17 ^{ISO DE DRV}
16 ^{ISO COM2}
15 ^{ISO RO LED}
EXTERNAL RS-485/RS-422 WIRING
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
TWISTED PAIR
TO OTHER TRANSCEIVERS
B
R_L
SHIELD (OPTIONAL)
A
TWISTED PAIR
TO OTHER TRANSCEIVERS
SH
R_L
SHIELD (OPTIONAL)
R7
100Ω
NOTE: RESISTOR R7 PROTECTS
THE MAX1480A/B/C FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
LOGIC GROUND ISOLATION BARRIER
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.
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