MAX1490EACPG Maxim Integrated, MAX1490EACPG Datasheet - Page 11

• Manufacturer Part Number: MAX1490EACPG
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated

Specifications of MAX1490EACPG

• Data Rate: 2.5 Mbps
• Operating Supply Voltage: 5 V
• Supply Current: 180 mA
• Operating Temperature Range: 0 C to + 70 C
• Mounting Style: Through Hole
• Package / Case: PDIP-24
• Maximum Power Dissipation: 696 mW

Figure 2. MAX1490EA/MAX1490EB Detailed Block Diagram and Typical Application Circuit
Table 2. Pullup and LED Drive Resistors for Figure 2
The MAX1480EC/MAX1490EB are slew-rate-limited,
minimizing EMI and reducing reflections caused by
improperly terminated cables. Figure 11 shows both
the driver output waveform of a MAX1480EA/
MAX1490EA transmitting a 150kHz signal and the
Fourier analysis of that waveform. High-frequency har-
monics with large amplitudes are evident. Figure 12
shows the same information for the slew-rate-limited
RO
MAX1490EA
MAX1490EB
DI
±15kV ESD-Protected, Isolated RS-485/RS-422
*SEE TABLE 2.
FS
OR EQUIVALENT
+5V
V
IN
74HC86
PART
1.07MHz/
1.45MHz
RECEIVER OUTPUT
DRIVER INPUT
OSC
C1
22µF
Reduced EMI and Reflections
______________________________________________________________________________________
V
CC3
T F/F
C2
0.1µF
MAX1480EC/MAX1490EB:
DI
´
Q
Q
R1*
R2*
SD
LOGIC GROUND
GND1
GND2
V
V
V
V
CC1
CC2
CC3
CC4
D1
SD
D2
FS
R0
R1 (Ω)
DI
200
200
MAX845
10
11
12
1
2
3
4
5
6
7
9
8
ISOLATION BARRIER
MAX1490EA/
MAX1490EB
270 pF
4kV
N
GND1
N
D1
D2
24
23
22
21
20
19
18
17
16
15
14
13
ISO RO DRV
ISO DI DRV
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
ISO RO DRV
A
B
Z
Y
ISO COM1
ISO DI DRV
ISO V
ISO RO LED
ISO V
CC2
CC1
R2 (Ω)
1000
3000
R3*
MAX1480EC/MAX1490EB transmitting the same signal.
The high-frequency harmonics have much lower ampli-
tudes, and therefore the potential for EMI is significantly
reduced.
There are two mechanisms to prevent excessive output
current and power dissipation caused by faults or by
bus contention. A foldback current limit on the output
stage provides immediate protection against short cir-
MAX1490EA: MAX490E
MAX1490EB: MAX488E
R4*
ISOLATED COMMON
D
R
R5, 100Ω
R6, 100Ω
Data Interfaces
SH1
SH2
A
Y
R3 (Ω)
B
Z
EXTERNAL RS-485/RS-422 WIRING
330
330
A
B
Z
Y
NOTE: RESISTORS R5 AND R6 PROTECT
THE MAX1490EA/MAX1490EB FROM
TRANSIENT CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
R
Driver Output Protection
L
R
L
TO OTHER TRANSCEIVERS
TO OTHER TRANSCEIVERS
(ONE RESISTOR ON EACH END)
SHIELD (OPTIONAL)
SHIELD (OPTIONAL)
TERMINATING RESISTOR
TWISTED PAIR
TWISTED PAIR
R4 (Ω)
1000
3000
R
R
L
L
11