MAX491ESD Maxim Integrated Products, MAX491ESD Datasheet - Page 8

• Manufacturer Part Number: MAX491ESD
• Description: RS-422/RS-485 Interface IC
• Manufacturer: Maxim Integrated Products

Specifications of MAX491ESD

• Case: SOP
• Lead Free Status / Rohs Status: No

The MAX481/MAX483/MAX485/MAX487–MAX491 and
MAX1487 are low-power transceivers for RS-485 and RS-
422 communications. The MAX481, MAX485, MAX490,
MAX491, and MAX1487 can transmit and receive at data
rates up to 2.5Mbps, while the MAX483, MAX487,
MAX488, and MAX489 are specified for data rates up to
250kbps. The MAX488–MAX491 are full-duplex trans-
ceivers while the MAX481, MAX483, MAX485, MAX487,
and MAX1487 are half-duplex. In addition, Driver Enable
(DE) and Receiver Enable (RE) pins are included on the
MAX481, MAX483, MAX485, MAX487, MAX489,
MAX491, and MAX1487. When disabled, the driver and
receiver outputs are high impedance.
Low-Power, Slew-Rate-Limited
RS-485/RS-422 Transceivers
Figure 2. MAX488/MAX490 Pin Configuration and Typical Operating Circuit
Figure 3. MAX489/MAX491 Pin Configuration and Typical Operating Circuit
8
__________Applications Information
TOP VIEW
TOP VIEW
_______________________________________________________________________________________
GND
GND
N.C.
GND
V
RO
DE
V
RE
DI
RO
RO
CC
CC
DI
B
A
1
2
3
4
5
6
7
1
2
3
4
1
2
3
4
DIP/SO
D
DIP/SO
MAX488
MAX490
R
μMAX
R
D
14
13
12
11
10
9
8
8
7
6
5
8
7
6
5
V
N.C.
A
B
Z
Y
N.C.
Z
Y
GND
DI
A
B
Z
Y
CC
RO
NC
DI
1, 8, 13
RO
DI
3
2
5
2
D
D
DE
V
4
GND
4
CC
3
1
RE GND
NOTE: TYPICAL OPERATING CIRCUIT SHOWN WITH DIP/SO PACKAGE.
R
R
V
CC
14
The 48kΩ,
MAX487 and MAX1487 allows up to 128 transceivers
on a bus, compared to the 1-unit load (12kΩ input
impedance) of standard RS-485 drivers (32 trans-
ceivers maximum). Any combination of MAX487/
MAX1487 and other RS-485 transceivers with a total of
32 unit loads or less can be put on the bus. The
MAX481/MAX483/MAX485 and MAX488–MAX491 have
standard 12kΩ Receiver Input impedance.
6, 7
9
10
12
11
5
6
8
7
B
Y
Z
A
Y
A
Z
B
Rt
Rt
1
/
4
-unit-load receiver input impedance of the
MAX489
MAX491
MAX488
MAX490
128 Transceivers on the Bus
Rt
Rt
MAX487/MAX1487:
V
CC
GND
R
R
RE
GND
V
CC
DE
D
D
RO
DI
RO
DI