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SP505_00_08308

a load of 00Ω. The signal levels and drive

capability of these drivers allow the drivers to

also support RS-485 requirements of ±.5V

minimumdifferentialoutputlevelswitha54Ω

load. The driver is designed to operate over

a common mode range of +2V to -7V, which

follows the RS-485 specification. This also

covers the +7V to -7V common mode range

for V. (RS-422) requirements. The V.

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 00Ω.

With the help of internal resistor networks,

the drivers achieve the 50Ω to 50Ω source

impedance and the 35Ω to 65Ω 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.(RS-422)andV.35,canoperate

over 0Mbps.

Driver Enable and Input

AllthedriversintheSP505containindividual

enablelineswhichcantri-statethedriverout-

puts when a logic "" is applied. This simpli-

fieshalf-duplexconfigurationsforsomeappli-

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

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 ofthe drivers is changed,

the electrical characteristics will change to

support the requirements of clock, data, and

control line signal levels. Table  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., V.0 and V.35.

V.28 Drivers

TheV.28driversoutputsingle–endedsignals

with a minimum of +5V (with 3kΩ & 2500pF

loading),andcanoperatetoatleast20kbps

under full load. Since the SP505 uses a

charge pump to generate the RS-232 output

rails, the driver outputs will never exceed

+0V. 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.0 (RS-423) drivers are also single–

endedsignalswhichproduceopencircuitV

OL

and V

Whenterminatedwitha450Ωloadtoground,

the driver output will not deviate more than

0% of the open circuit value. This is in

compliance of the ITU V.10 specification.

The V.0 drivers are used in RS-449, EIA-

530, EIA-530Aand V.36 modes as Category

II signals from each of their corresponding

specifications.

V.11 Drivers

The third type of driver is a V. (RS-422)

type differential driver. Due to the nature of

differential signaling, the drivers are more

immunetonoiseasopposedtosingle-ended

transmissionmethods. Theadvantageisevi-

dentoverhighspeedsandlongtransmission

lines. The strength of the driver outputs can

producedifferentialsignalsthatcanmaintain

typically +2.2V differential output levels with