參數(shù)資料
型號: SP495CT
英文描述: Quad Differential RS-485 Transceiver
中文描述: 四路差分的RS - 485收發(fā)器
文件頁數(shù): 5/6頁
文件大?。?/td> 60K
代理商: SP495CT
5
SP495
Quad Differential RS-485 Transceiver
Copyright 2000 Sipex Corporation
+3V
0V
RE
5V
R
0V
1.5V
1.5V
t
ZL
t
ZH
f = 1MHz; t
R
< 10ns; t
F
< 10ns
R
1.5V
1.5V
t
LZ
t
HZ
0.5V
0.5V
Output normally LOW
Output normally HIGH
V
IL
V
IH
Figure 9. Receiver Enable and Disable Times
DESCRIPTION
General Description...
The
SP495
is a quad differential transceiver that
meets the requirements of RS-485, RS-422, and
differential SCSI at data rates to beyond 10Mbps.
Fabricated with a proprietary Sipex BiCMOS
process, the
SP495
requires only a fraction of the
power of older bipolar designs.
The
SP495
features three half-duplex transceivers
suitable for data bus connections and a fourth
full-duplex transceiver with independent enables
ideal for use as a control bus transceiver. A
complete SCSI initiator or target interface can be
implemented using five
SP495
s.
The RS-485 standard is ideal for multi-drop
applications and for long-distance interfaces.
RS-485 allows up to 32 drivers and 32 receivers
to be connected to a single data bus, making it an
ideal choice for multi-drop applications. Since
the cabling can be as long as 4,000 feet, RS-485
transceivers are specified for operation with a
wide (-7V to +12V) common mode range to
accommodate ground potential differences.
Because RS-485 is a low impedance differential
interface, data is virtually immune to noise in the
transmission line.
Drivers...
The differential drivers for the
SP495
have typical
output voltage swings (no load) of 0 to +5Volts.
With loading to the RS-485 specification (54
),
drivers must maintain outputs greater than 1.5V.
The three half-duplex drivers of the
SP495
have
independent Driver Enable control lines which
are active HIGH. A logic HIGH on DEx (pins 1,
4, or 5 of the
SP495
) will enable the addressed
differential driver output. A logic LOW on DEx
will tri-state the driver output and enable the
receiver. The fourth driver is controlled by its
own DE4 Enable line and can be used in half -
duplex or full-duplex modes.
Receivers...
The differential receivers for the
SP495
have an
input sensitivity of
±
200mV. Input impedance is
typically 15k
(12k
minimum). A wide
common mode range of -7V to +12V allows for
large ground potential differences between widely
separated systems. These receivers are equipped
with a fail-safe feature which guarantees that the
receiver output will be in a HIGH state when the
input is left unconnected (note: this feature
operates with floating inputs, not terminated
inputs).
Like the half-duplex drivers, the three half-duplex
receivers of the
SP495
have independent Re-
ceiver Enable control lines which are active
LOW. A logic LOW on REx (pins 1, 4, or 5 of
the
SP495
) enables the differential receivers. A
logic HIGH on REx tri-states the receivers. The
fourth receiver is controlled by its own RE4
Enable line and can be used in half-duplex or
full-duplex modes.
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