SP505 Datasheet, PDF (20/35 Pages) Sipex Corporation – WAN Multi-Mode Serial Transceiver

Drivers
The SP505 has seven (7) enhanced independent
drivers. Control for the mode selection is done
via a four–bit control word. The drivers are
prearranged such that for each mode of opera-
tion, the relative position and functionality of
the drivers are set up to accommodate the se-
lected interface mode. As the mode of the driv-
ers is changed, the electrical characteristics will
change to support the requirements of clock,
data, and control line signal levels. Table 1
shows the mode of each driver in the different
interface modes that can be selected.
There are four basic types of driver circuits —
V.28, V.11, V.10 and V.35.
V.28 Drivers
The V.28 drivers output single–ended signals
with a minimum of +5V (with 3kΩ & 2500pF
loading), and can operate to at least 120kbps
under full load. Since the SP505 uses a charge
pump to generate the RS-232 output rails, the
driver outputs will never exceed +10V. The
V.28 drivers are used in RS-232 mode for all
signals, and also in V.35 mode where four (4)
drivers are used as the control line signals (DTR,
RTS, LL, and RL).
V.10 Drivers
The V.10 (RS-423) drivers are also single–
ended signals which produce open circuit V_OL
and V_OH measurements of +4.0V to +6.0V.
When terminated with a 450Ω load to ground,
the driver output will not deviate more than 10%
of the open circuit value. This is in compliance
of the ITU V.10 specification. The V.10 drivers
are used in RS-449, EIA-530, EIA-530A and
V.36 modes as Category II signals from each of
their corresponding specifications.
V.11 Drivers
The third type of driver is a V.11 (RS-422) type
differential driver. Due to the nature of differ-
ential 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 typically +2.2V differ-
ential output levels with a load of 100Ω. The
signal levels and drive capability of these driv-
ers allow the drivers to also support RS-485
requirements of ±1.5V minimum differential
output levels with a 54Ω load. The driver is
designed to operate over a common mode range
of +12V to -7V, which follows the RS-485
specification. This also covers the +7V to -7V
common mode range for V.11 (RS-422) re-
quirements. The V.11 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 signals.
V.35 Drivers
The fourth type of driver is the V.35 driver.
These drivers were specifically designed to com-
ply with the requirements of V.35. Unique to
the industry, the Sipex's V.35 driver architec-
ture used in the SP505 does not need external
termination resistors to operate and comply with
V.35. This simplifies existing V.35 implemen-
tations that use external termination schemes.
The V.35 drivers can produce +0.55V driver
output signals with minimum deviation (maxi-
mum 20%) given an equivalent load of 100Ω.
With the help of internal resistor networks, the
drivers achieve the 50Ω to 150Ω source imped-
ance and the 135Ω to 165Ω short-circuit imped-
ance for V.35. The V.35 driver is disabled and
transparent when the decoder is in all other
modes. All of the differential drivers; V.11 (RS-
422) and V.35, can operate over 10Mbps.
Driver Enable and Input
All the drivers in the SP505 contain individual
enable lines which can tri-state the driver out-
puts when a logic "1" is applied. This simplifies
half-duplex configurations for some applica-
tions and also provides simpler DTE/DCE
flexibility with one integrated circuit.
The driver inputs are both TTL or CMOS
compatible. 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 not be left floating.
Receivers
The SP505 has seven (7) independent receivers
which can be programmed for the different
interface modes. Control for the mode selection
is done via a 4–bit control word, which is the
same as the driver's 4-bit control word.
Like the drivers, the receivers are prearranged
for the specific requirements of the synchronous
Rev: A Date: 1/27/04
SP505 Multi–Mode Serial Transceiver
20
© Copyright 2004 Sipex Corporation