MAX1480E Datasheet, PDF (10/19 Pages) Maxim Integrated Products – 15kV ESD-Protected, Isolated RS-485/RS-422

±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
V_CC3
Q
FS
OSC
1.07MHz/
T F/F
1.45MHz
Q
MAX845E
D1
N
D2
N
SD
GND1
ISO DI IN
ISO DE IN
ISO RO DRV
ISO V_CC1
MAX1480EA: MAX1487E
MAX1480EC: MAX487E
B
D
A
R
RE
VIN
+5V
C1
C2
22µF
0.1µF
74HC86
OR EQUIVALENT
DI
DRIVER INPUT
R1*
DI´
R2*
DE
DRIVER ENABLE
DE´
R3*
RECEIVER OUTPUT
RO
*SEE TABLE 1.
LOGIC GROUND
ISO COM1
EXTERNAL RS-485/RS-422 WIRING
VCC1 ₁
VCC2 ₂
MAX1480EA
MAX1480EC
28 AC1 (MAKE NO CONNECTION)
27 AC2 (MAKE NO CONNECTION)
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
TWISTED PAIR
TO OTHER TRANSCEIVERS
D1 3
D2 4
GND1 ₅
FS 6
SD ₇
VCC3 ₈
DI ₉
MAX845E
MAX1487E
MAX487E
26 ^{ISO VCC1}
B
25
24 ^{ISO RO DRV}
23 ^A
22 ^{ISO DI IN}
21 ^{ISO DE IN}
20 ^{ISO COM1}
B
A
R6*
SH
R4*
RL
SHIELD (OPTIONAL)
TWISTED PAIR
TO OTHER TRANSCEIVERS
RL
SHIELD (OPTIONAL)
VCC4 ₁₀
DE ₁₁
GND2 ₁₂
RO ₁₃
VCC5
14
19 ^{ISO DI DRV}
18 ^{ISO VCC2}
17 ^{ISO DE DRV}
16 ^{ISO COM2}
15 ^{ISO RO LED}
R5*
NOTE: RESISTOR R7 PROTECTS
R7
100Ω
THE MAX1480EA FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
ISOLATION BARRIER
ISOLATED COMMON
270pF
4kV
Figure 1. MAX1480EA/MAX1480EC Detailed Block Diagram and Application Circuit
Table 1. Pullup and LED Drive Resistors for Figure 1
PART
MAX1480EA
MAX1480EC
R1 (Ω)
200
200
R2 (Ω)
200
200
R3 (Ω)
1000
3000
R4 (Ω)
4300
3000
R5 (Ω)
1000
3000
R6 (Ω)
200
200
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.
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