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

Drivers
The SP505 has seven (7) enhanced in-
dependent drivers. Control for the mode
selection is done via a four–bit control word.
The drivers are prearranged such that for
each mode of operation, the relative posi-
tion and functionality of the drivers are set
up to accommodate the selected interface
mode. As the mode of the drivers 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
differential signaling, the drivers are more
immune to noise as opposed to single-ended
transmission methods. The advantage is evi-
dent over high speeds and long transmission
lines. The strength of the driver outputs can
produce differential signals that can maintain
typically +2.2V differential output levels with
a load of 100Ω. The signal levels and drive
capability of these drivers 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) requirements. 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 comply with the requirements of V.35.
Unique to the industry, the Sipex's V.35
driver architecture used in the SP505 does
not need external termination resistors to
operate and comply with V.35. This simpli-
fies existing V.35 implementations that use
external termination schemes. The V.35
drivers can produce +0.55V driver output
signals with minimum deviation (maximum
20%) given an equivalent load of 100Ω.
With the help of internal resistor networks,
the drivers achieve the 50Ω to 150Ω source
impedance and the 135Ω to 165Ω short-cir-
cuit impedance 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 simpli-
fies half-duplex configurations for some appli-
cations 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 out-
put will be at a defined state. Unused driver
inputs should not be left floating.
Receivers
The SP505 has seven (7) independent re-
ceivers which can be programmed for the
different interface modes. Control for the
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SP505_100_081308