MAX1490EBCPG+ Maxim Integrated Products, MAX1490EBCPG+ Datasheet - Page 17

• Manufacturer Part Number: MAX1490EBCPG+
• Description: IC RS485/RS422 DATA INTRFC 24DIP
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX1490EBCPG+

• Number Of Drivers/receivers: 1/1
• Protocol: RS422, RS485
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Through Hole
• Package / Case: 24-DIP (0.600", 15.24mm)
• Data Rate: 250 Kbps
• Operating Supply Voltage: 5 V
• Supply Current: 130 mA
• Operating Temperature Range: 0 C to + 70 C
• Maximum Power Dissipation: 696 mW
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MAX1480EC/MAX1490EA/MAX1490EB. Connections
• A shield trace connected to the ground on each side
• Try to maximize the width of the isolation barrier
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
are specified and characterized using the resistor val-
ues shown in Tables 1 and 2. Altering the recommend-
ed values can degrade performance.
DI and DE are intended to be driven through a series
current-limiting resistor. Directly grounding these
pins destroys the device.
The DI and DE (MAX1480EA/MAX1480EC only) inputs
are the cathodes of LEDs whose anodes are connected
to the supply. These points are best driven by a CMOS-
logic gate with a series resistor to limit the current. The
Figure 16. Typical Full-Duplex RS-485/RS-422 Network
RO
DI
OR EQUIVALENT
and components from one side should not be locat-
ed near those of the other side.
of the barrier can help intercept capacitive currents
that might otherwise couple into the signal path. In a
double-sided or multilayer board, these shield traces
should be present on all conductor layers.
wherever possible; a clear space of at least 0.25
inches between ground and isolated common is
suggested.
+5V
±15kV ESD-Protected, Isolated RS-485/RS-422
V
74HC86
IN
DRIVER INPUT
C1
22µF
RECEIVER OUTPUT
Pullup and LED Drive Resistors
DI
´
______________________________________________________________________________________
R1
C2
0.1µF
R2
GND1
GND2
LOGIC GROUND
V
V
V
V
CC1
CC2
CC3
CC4
D1
D2
SD
RO
FS
DI
10
11
12
1
2
3
4
5
6
7
8
9
ISOLATION BARRIER
MAX1490EA/
MAX1490EB
270pF
4kV
24
23
22
21
20
19
18
17
16
15
14
13
ISO V
A
B
Z
ISO COM1
ISO DI DRV
ISO V
ISO RO LED
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
ISO RO DRV
Y
CC1
CC2
R3
ISOLATED COMMON
R4
resistor values shown in Tables 1 and 2 are recommend-
ed when the 74HC86 gate or equivalent is used. These
values may need to be adjusted if a driving gate with dis-
similar series resistance is used.
All pullup resistors are based on optocoupler specifica-
tions in order to optimize the devices’ data-transfer rates.
The isolated common may be completely floating with
respect to the logic ground and the effective network
ground. The receiver input resistors cause the isolated
common voltage to go to the mean voltage of the receiver
inputs. If using shielded cable, connect the isolated com-
mon to the shield through a 100Ω resistor. In the case of
the MAX1490EA/MAX1490EB, each shield should have its
own 100Ω resistor (Figures 1, 2, 15, and 16).
The RS-422/RS-485 standard is specified for cable
lengths up to 4000 feet. When approaching or exceeding
the specified maximum cable length, a ground-potential
difference of several tens of volts can easily develop.
This difference can be either DC, AC, at power-line fre-
quency, or any imaginable noise or impulse waveform. It
is typically very low impedance so that if a connection
between the two grounds is attempted, very large cur-
R5, 100Ω
R6, 100Ω
SH1
SH2
Double-Isolated RS-485 Repeater
A
Y
B
Z
NOTE: RESISTORS R5 AND R6 PROTECT
THE MAX1490EA/MAX1490EB FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
Isolated Common Connection
Data Interfaces
120Ω
120Ω
SHIELD (OPTIONAL)
SHIELD (OPTIONAL)
120Ω
120Ω
Y
Z
B
A
D
R
DI
RO
17