MAX1480BCPI Maxim Integrated Products, MAX1480BCPI Datasheet - Page 19

• Manufacturer Part Number: MAX1480BCPI
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated Products

Specifications of MAX1480BCPI

• Data Rate: 250 Kbps
• Operating Supply Voltage: 5 V
• Supply Current: 95 mA
• Operating Temperature Range: 0 C to + 70 C
• Package / Case: PDIP-28
• Maximum Power Dissipation: 727 mW
• Mounting Style: Through Hole
• Supply Voltage (max): 5.5 V
• Lead Free Status / Rohs Status: No

• A shield trace connected to the ground on each side
• Try to maximize the width of the isolation barrier
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B are specified and characterized using the
resistor values shown in Table 1 of Figure 1 and Table
2 of Figure 2. Altering the recommended values can
degrade performance.
Figure 15. Doubly Isolated RS-485 Repeater
NETWORK SEGMENT A
Connections and components from one side should
not be located 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.
3kΩ
200Ω
A
B
Pullup and LED Drive Resistors
3kΩ
23
25
26
15
______________________________________________________________________________________
19
22
17
21
24
MAX1480C
+5V
2 8
Complete, Isolated RS-485/RS-422
5 7 12
10 14
13
11
9
2 B
1
+5V
A
200Ω
200Ω
16
51kΩ
74HC123
CLR
3kΩ
3
1000pF
DRIVER
ENABLE
B > A
15
Q
Q
14
13
4
4
1
74HC04
The DI and DE (MAX1480A/B/C 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 resis-
tor values shown in Tables 1 and 2 are recommended
when the 74HC86 gate or equivalent is used. These
values may need to be adjusted if a driving gate with
dissimilar series resistance is used.
All pull-up 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 will cause the iso-
lated common voltage to go to the mean voltage of the
receiver inputs. If using shielded cable, connect the
isolated common to the shield through a 100Ω resistor.
In the case of the MAX1490, each shield should have
its own 100Ω resistor (Figures 1, 2, 13, and 14).
3
2
10 B
+5V
9
A
DRIVER
ENABLE
A > B
51kΩ
74HC123
CLR
3kΩ
11
200Ω
1000pF
7
200Ω
Q
Q
6
5
12
9
13
11
Isolated Common Connection
2 8 10 14
5 7 12
Data Interface
MAX1480C
+5V
19
22
17
21
15
23
25
26
24
3kΩ
200Ω
A
B
NETWORK SEGMENT B
3kΩ
19