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SP304

RS-232/RS-422 Line Drivers/Receivers

Signal Processing Technologies 

PIN ASSIGNMENTS

VDD (+12V) 1

RIA2 2

RIA1 3

TOA2 4

TOA1 5

SELECT A 6

SELECT B 7

TOB1 8

TOB2 9

RIB1 10

RIB2 11

GND 12

24 VCC (+5V)

23 ROA2

22 ROA1

21 TIA2

20 TIA1

19 LB

18 N.C.

17 TIB1

16 TIB2

15 ROB1

14 ROB2

13 VEE (-12V)

VDD (+12V) 1

RIA2 2

RIA1 3

N.C. 4

TOA2 5

TOA1 6

SELECT A 7

SELECT B 8

TOB1 9

TOB2 10

N.C. 11

RIB1 12

RIB2 13

GND 14

28 VCC (+5V)

27 ROA2

26 ROA1

25 N.C.

24 TIA2

23 TIA1

22 LB

21 N.C.

20 TIB1

19 TIB2

18 N.C.

17 ROB1

16 ROB2

15 VEE (-12V)

FEATURES…

The SP304 is a proprietary single-chip device

that contain both RS-232 and RS-422 protocol

line drivers and receivers. It is pin–for–pin com-

patible with the Sipex SP302. Like the SP302,

its configuration may be changed at any time by

logic levels on two control lines. In any configu-

ration, the SP304 fully meets the requirements

of both the EIA RS-232D and RS-422 data

communication standards. The SP304 enhance-

ments include improved isolation from external

signals and a true high–impedance driver output

in the loopback test mode, and no power up

sequence requirements.

The RS-232 line driver circuits convert TTL

logic level inputs into inverted RS-232 output

signals. The RS-422 line drivers convert TTL

logic levels into RS-422 differential output sig-

nals. The RS-422 line driver outputs feature

high source and sink current capability. All line

drivers are internally protected against short

circuits on their outputs.

The RS-232 receivers convert the EIA RS-232

input signals to inverted TTL output logic lev-

els. The RS-422 receivers convert the EIA RS-

422 differential input signals into non-inverted

TTL output logic levels. Receiver input filtering

provides excellent high frequency noise immu-

nity. Input pulses with widths less than 1µs are

completely ignored. The RS-232 receivers have

the additional feature of voltage hysteresis, which

helps eliminate spurious output transitions that

might result from low amplitude noise voltages

during slower-speed signal transitions.

A loopback test mode is provided that puts the

driver outputs to a high impedance tri-state

level, and routes the driver outputs to their

associated receiver inputs. In this configuration,

the signal path is non-inverting from the TTL

driver input to the receiver TTL output. This

operating mode allows the controlling system to

perform diagnostic self-test of the RS-232/

RS-422 driver/receiver circuitry at speeds up to

3,000 bits per second. In the loopback mode a

±13.2V input range may be applied to the re-

ceiver inputs with no interference to the loopback

test. In addition, the driver outputs are in a true

high–impedance state during loopback.

The SP304 is available in 24-pin single width

(0.300") plastic DIP and 28-pin SOIC packages,

for operation over the commercial and indus-

trial temperature ranges.

USING THE SP304

POWER SUPPLIES

The SP304 requires ±12V and +5V for full

RS-232 and RS-422 operation. The ±12V sup-

plies set up the RS-232 ±9V voltage swings, and

the +5V is used for the internal logic that for-

mats the communications mode and controls the

loopback function. The supply voltages can be

decreased to as low as ±7V for VDD and VEE, and

80

Corporation

SIGNAL PROCESSING EXCELLENCE

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