SP508 datasheet(21/27 Pages) SIPEX

21 / 27 page

Date: 8/19/04

SP508 Enhanced WAN Multi–Protocol Serial Transceiver

The SP508 contains highly integrated serial

transceivers that offer programmability between

interface modes through software control. The

SP508 offers the hardware interface modes for

RS-232 (V.28), RS-449/V.36 (V.11 and V.10),

EIA-530 (V.11 and V.10), EIA-530A (V.11 and

V.10), V.35 (V.35 and V.28) and X.21(V.11). The

interface mode selection is done via three control

pins, which can be latched via microprocessor

control.

The SP508 has eight drivers, eight receivers, and

Sipex's patented on-board charge pump (5,306,954)

that is ideally suited for wide area network

connectivity and other multi-protocol applications.

Other features include digital and line loopback

modes, individual enable/disable control lines for

each driver and receiver, fail-safe when inputs are

either open or shorted, individual termination

resistor ground paths, separate driver and receiver

ground outputs, enhanced ESD protection on driver

outputs and receiver inputs.

THEORY OF OPERATION

The SP508 device is made up of 1) the drivers, 2)

the receivers, 3) a charge pump, 4) DTE/DCE

switching algorithm, and 5) control logic.

Drivers

The SP508 has eight enhanced independent drivers.

Control for the mode selection is done via a three-

bit control word into D0, D1, and D2. The drivers

are prearranged such that for each mode of

operation, the relative position 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 required signal levels. The mode of

each driver in the different interface modes that

can be selected is shown in Table 1.

There are four basic types of driver circuits –

ITU-T-V.28 (RS-232), ITU-T-V.10 (RS-423),

ITU-T-V.11 (RS-422), and CCITT-V.35.

The V.28 (RS-232) drivers output single-ended

signals with a minimum of +5V (with 3k

Ω &

2500pF loading), and can operate over 120kbps.

Since the SP508 uses a charge pump to generate

the RS-232 output rails, the driver outputs will

never exceed +10V. The V.28 driver architecture

is similar to Sipex's standard line of RS-232

transceivers.

The RS-423 (V.10) drivers are also single-ended

signals which produce open circuit V

OL and VOH

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 (RS-423) drivers are used

in RS-449/V.36, EIA-530, and EIA-530A modes

as Category II signals from each of their

corresponding specifications. The V.10 drivers

are guaranteed to transmit over 120kbps, but can

operate at over 1Mbps if necessary.

The third type of drivers are V.11 (RS-422)

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 +2V differential output levels with a load

of 100

Ω. The signal levels and drive capability of

these drivers allow the drivers to also support

RS-485 requirements of +1.5V differential output

levels with a 54

Ω load. The strength allows the

SP508 differential driver to drive over long cable

lengths with minimal signal degradation. 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. Sipex's new driver design

over its predecessors allow the SP508 to operate

over 20Mbps for differential transmission.

FEATURES

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