北京国华芯达电子公司外围电路开发工具max1487

_______________General Description
MAX1487 is a low power differential bus transceiver
designed to meet the requirements of RS-485 standard
for multipoint data transmission. In addition it is
compatible with TIA/EIA-422-B.
The CMOS design offers significant power savings
over its bipolar counter parts.
Device feature fail-safe circuitry, which guarantees a
logic-high receiver output when the receiver inputs are
open or shorted. This means that the receiver output
will be logic high if all transmitters on a terminated bus
are disabled.
These transceivers typically draw 375μA of supply
current when unloaded, or when fully loaded with the
drivers disabled. 　MAX1487 is ideal for RS485
communication.
______________________Applications
PLC
Industrial PC
Industrial area network
DTE/DCE
Point of sales
Security
Data Log system
______________Ordering Information

Part Number	Temperature range	Package
MAX1487EESA	-40℃ To +85℃	8 SO
MAX1487EEPA	-40℃ To +85℃	8 Plastic DIP

　　　　_________________________Features
　　　　Fail Safe Bi-directional Fail safe transceiver
　　　　100% RS-485 device compliant
　　　　Low power CMOS design: ICC 500 μA max.
　　　　Suitable for multipoint long distance serial
　　　　communication in noisy environment
　　　　3-state driver & receiver output.
　　　　Independent Driver/Receiver Enable Pin
　　　　Wide common mode range: –7V to 12V
　　　　Driver output ±60mA Max
　　　　Thermal Shutdown
　　　　Bi-directional current limit for driver
　　　　1/8 unit load: 256 nodes
　　　　Receiver sensitivity threshold:
　　　　-200mV/-50mV
　　　　HBM ESD level exceed 15KV
　　　　SO-8 package available
　　　　Drop in replacement for : MAX1487, SN75176
　　　　________________Pin Configurations

MAX1487 Failsafe RS485 Transceiver

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (VCC) ........................………………........7V
Control Input Voltage (/RE, DE)……-0.3V to (VCC + 0.3V)
Driver Input Voltage (DI) ........………-0.3V to (VCC + 0.3V)
Driver Output Voltage (A, B).......……………-7.5V to 12.5V
Receiver Input Voltage (A, B) .........…………-7.5V to 12.5V
Receiver Output Voltage (RO).………-0.3V to (VCC + 0.3V)
Continuous Power Dissipation (TA = +70°C)

8-Pin Plastic DIP (derate 9.09mW/°C above +70°C..727mW
8-Pin SO (derate 5.88mW/°C above +70°………471mW
Operating Temperature Ranges
MAX1487EE_ _.........................…………-40°C to +85°C
Storage Temperature Range …………-65°C to +160°C
Lead Temperature (soldering, 10sec)………………+300°C

Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device.
These are stress ratings only, and functional operation of the device at these or any other conditions beyond those
indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS
（ VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.）

MAX1487 Failsafe RS485 Transceiver

SWITCHING CHARACTERISTICS
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)

MAX1487 Failsafe RS485 Transceiver

_______________Detailed Description
The MAX1487 high-speed transceivers for RS-485/
RS-422 communication contain one driver and one
receiver. The device features fail-safe circuitry, which
guarantees a logic-high receiver output when the
receiver inputs are open or shorted, or when they are
connected to a terminated transmission line with all
drivers disabled. The MAX1487 features reduced slewrate
drivers that minimize EMI and reduce reflections
caused by improperly terminated cables, allowing
error-free data transmission up to 500 KBPS .
The part operate from a single +5V supply. Drivers are
output short-circuit current limited. Thermal shutdown
circuitry protects drivers against excessive power
dissipation. When activated, the thermal shutdown
circuitry places the driver outputs into a high impedance
state.
Receiver Input Filtering
The receiver of the MAX1487, incorporates input filtering
in addition to input hysteresis. This filtering enhances
noise immunity with differential signals that have very
slow rise and fall times.

The MAX1487 family guarantees a logic-high receiver
output when the receiver inputs are shorted or open, or
when they are connected to a terminated transmission
line with all drivers disabled. This is done by setting the
receiver threshold between -50mV and -200mV. If the
differential receiver input voltage (A-B) is greater than
or equal to -50mV, RO is logic high. If A-B is less than
or equal to -200mV, RO is logic low. In the case of a
terminated bus with all transmitters disabled, the
receiver’s differential input voltage is pulled to 0V by
the termination. With the receiver thresholds of the
MAX1487 family, this results in a logic high with a 50mV
minimum noise margin. Unlike previous fail-safe
devices, the -50mV to -200mV threshold complies with
the ±200mV EIA/TIA-485 standard.
256 Transceivers on the Bus
The MAX1487 transceiver have a 1/8-unit -load receiver
input impedance (96k), allowing up to 256 transceivers
to be connected in parallel on one communication line.
Any combination of these devices and/or other RS-485
transceivers with a total of 32 unit loads or less can be
connected to the line.

MAX1487 Failsafe RS485 Transceiver

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