SP505 datasheet(20/35 Pages) SIPEX

20 / 35 page

Rev: A Date: 1/27/04

SP505 Multi–Mode Serial Transceiver

requirements of ±1.5V minimum differential

output levels with a 54

Ω 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 100

Ω.

With the help of internal resistor networks, the

drivers achieve the 50

Ω to 150Ω source imped-

ance and the 135

Ω 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

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 3k

Ω & 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

and V

OH measurements of +4.0V to +6.0V.

When terminated with a 450

Ω 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 100

Ω. The

signal levels and drive capability of these driv-

ers allow the drivers to also support RS-485

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