ADM1487EARZ Analog Devices Inc, ADM1487EARZ Datasheet - Page 15

• Manufacturer Part Number: ADM1487EARZ
• Description: IC TXRX HALF DUP RS485/422 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Transceiverr

Specifications of ADM1487EARZ

• Number Of Drivers/receivers: 1/1
• Protocol: RS422, RS485
• Voltage - Supply: 4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
DIFFERENTIAL DATA TRANSMISSION
Differential data transmission is used to reliably transmit data
at high rates over long distances and through noisy environ-
ments. Differential transmission nullifies the effects of ground
shifts and noise signals that appear as common-mode voltages
on the line. There are two main standards approved by TIA/EIA
that specify the electrical characteristics of transceivers used in
differential data transmission.
The RS-422 standard specifies data rates up to 10 MB and line
lengths up to 4000 feet. A single driver can drive a transmission
line with up to 10 receivers.
To cater to true multipoint communications, the RS-485 standard
is defined. This standard meets or exceeds all the requirements
of RS-422, but also allows for up to 32 drivers and 32 receivers
to be connected to a single bus. An extended common-mode
range of −7 V to +12 V is defined. The most significant differ-
ence between RS-422 and RS-485 is that the drivers can be
disabled, thereby allowing as many as 32 drivers to be connected
to a single line. Only one driver is enabled at a time, but the
RS-485 standard contains additional specifications to guarantee
device safety in the event of line contention.
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CABLE AND DATA RATE
The transmission line of choice for RS-485 communications is
a twisted pair. A twisted pair cable can cancel common-mode
noise and can also cause cancellation of the magnetic fields
generated by the current flowing through each wire, thereby
reducing the effective inductance of the pair.
A typical application showing a multipoint transmission net-
work is illustrated in Figure 29. An RS-485 transmission line
can have as many as 32 transceivers on the bus. Only one driver
can transmit at a particular time, but multiple receivers can be
enabled simultaneously.
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T
ADM485E/ADM487E/ADM1487E
D
Figure 29. Typical RS-485 Network
R
D
R
R
T
R
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