SP526CF datasheet(16/23 Pages) SIPEX

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Rev: B Date:7/7/04

SP526 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 54

Ω. The signal levels and

drive capability of these drivers allow the driv-

ers to also support RS-422 (V.11) requirements

±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 400k

Ω.

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

Ω 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.

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