SP526 Datasheet, PDF (16/23 Pages) Sipex Corporation – WAN Multi-Mode Serial Transceiver

of the ITU V.10 specification. The RS-423
drivers are used in RS-449, EIA-530, EIA-530A
and V.36 modes as Category II signals from
each of their corresponding specifications.
The third and fourth type of drivers are RS-422
(V.11)/RS-485 type differential drivers. Due to
the nature of differential signaling, the drivers
are more immune to noise as opposed to single-
ended transmission methods. The advantage is
evident over high speeds and long transmission
lines. The strength of the driver outputs can
produce differential signals that can maintain
RS-485, ±1.5V differential output levels with a
worst case load of 54Ω. The signal levels and
drive capability of these drivers allow the driv-
ers to also support RS-422 (V.11) requirements
of ±2V differential output levels with 100Ω
loads. The driver is designed to operate over a
common mode range of +7V to -7V which
follows the V.11 specification. The RS-422
drivers are used in RS-449, EIA-530, EIA-530A
and V.36 modes as Category I signals which are
used for clock and data. All of the differential
drivers can operate to at least 10Mbps.
The drivers also have separate enable pins which
simplifies half-duplex configurations for some
applications and also provides simpler DTE/
DCE flexibility with one integrated circuit. The
enable pins will tri-state the drivers when the
ENT1, ENT2, ENT3, and ENT4 pins are at a
logic HIGH ("1"). During tri-stated conditions,
the driver outputs will be at a high impedance
state.
The driver inputs are both TTL or CMOS com-
patible. Each driver input should have a pull-
down or pull-up resistor so that the output will
be at a defined state. Unused driver inputs
should have pull-up resistors to +5V connected
so that the output is at a logic LOW ("0").
Unused driver inputs should not be left floating.
For differential drivers, the non-inverting out-
put will be at a logic HIGH ("1"). The typical
pull-up resistor value should be 400kΩ.
Receivers
The SP526 has four independent receivers which
can be programmed for the different interface
modes. Control for the mode selection is done
via a two–bit control word that is the same as the
driver control word. Therefore, if the modes for
the drivers and receivers are supposed to be
identical in the application, the control lines can
be tied together.
Like the drivers, the receivers are prearranged
for the specific requirements of the synchronous
serial interface. As the operating mode of the
receivers is changed, the electrical characteris-
tics will change to support the required serial
interface protocols of the receivers. Table 1
shows the mode of each receiver in the different
interface modes that can be selected.
There are two basic types of receiver circuits —
RS-232 (V.28) and RS-422 (V.11).
The RS-232 (V.28) receiver is single–ended and
accepts RS-232 signals from the RS-232 driver.
The RS-232 receiver has an operating voltage
range of ±15V and can receive signals downs to
±3V. The input sensitivity complies with RS-
232 and V.28 at ±3V. The input impedance is
3kΩ to 7kΩ in accordance to RS-232 and V.28.
The receiver output produces a TTL/CMOS
signal with a +2.4V minimum for a logic "1" and
a +0.8V maximum for a logic "0". RS-232(V.28)
receivers can be used in RS-232 mode for data,
clock or control signals. They are also used in
V.35 mode for control line signals: CTS, DSR,
LL, and RL. The RS-232 receivers can operate
to at least 120kbps.
Rev: B Date:7/7/04
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SP526 Multi–Mode Serial Transceiver
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© Copyright 2004 Sipex Corporation