SP231ADS/01

SP231A Enhanced RS-232 Line Drivers/Receivers

© Copyright 2000 Sipex Corporation

4

Figure 1. Charge Pump Voltage Doubler

Figure 2. Charge Pump Voltage Inverter

S1

GND

V

CC

+

V+ = 2V

CC

+

V

CC

S2

S3

S4

C1

C3

INTERNAL

OSCILLATOR

S1

FROM

VOLTAGE DOUBLER

V+

+

V- = -(V+)

+

S2

S3

S4

C2

C4

INTERNAL

OSCILLATOR

GND

GND

FEATURES…

The Sipex SP231A, SP232A and SP233A are

enhanced versions of the Sipex SP231, SP232

andSP233RS-232linedrivers/receivers.Theyarepin-

for-pin replacements for these earlier versions, will

operate in their sockets with capacitors ranging from

0.1 to 100

µF, either polarized or non–polarized, and

feature several improvements in both performance

and ease of use. Performance enhancements include

10V/

µs slew rate, 120k bits per second guaranteed

transmission rate, and increased drive current for

longerandmoreflexiblecableconfigurations.Easeof

useenhancementsincludesmaller,0.1

µFchargepump

capacitors, enhanced ESD protection, low power

dissipation and overall ruggedized construction for

commercial environments.

The SP232A, SP233A, SP310A and SP312A

include charge pump voltage converters which allow

them to operate from a single +5V supply. These

converters convert the +5V input power to the

±10V

needed to generate the RS-232 output levels. Both

meet all EIA RS-232D and CCITT V.28 specifica-

tions. The SP231A has provisions for external V+

supplies. With this power supplied externally, the

current drain due to charge pump operation is

considerably reduced, typically to 400

µA.

The SP310A provides identical features as the

SP232A. The SP310A has a single control line

which simultaneously shuts down the internal DC/

DC converter and puts all transmitter and receiver

outputs into a high impedance state. The SP312A

is identical to the SP310A with separate tri-state

and shutdown control lines.

The SP231A is available in 14-pin plastic DIP,

CERDIP and 16-pin SOIC packages for opera-

tion over commercial, industrial and military

temperature ranges. The SP232A is available

in 16-pin plastic DIP, SOIC and CERDIP

packages, operating over the commercial,

industrial and military temperature ranges. The

SP233A is available in a 20-pin plastic DIP and

20–pin SOIC package for operation over the

commercial and industrial temperature ranges.

The SP310A and SP312A are available in

18-pin plastic, CERDIP and SOIC packages

for operation over the commercial and industrial

temperature ranges. Please consult the factory

for DIP and surface-mount packaged parts

supplied on tape-on-reel, as well as parts screened

to MIL-M-38510.

THEORY OF OPERATION

The SP231A, SP232A, SP233A, SP310A and

SP312A devices are made up of three basic circuit

blocks – 1) a driver/transmitter, 2) a receiver and 3)

a charge pump. Each block is described below.

Driver/Transmitter

The drivers are inverting transmitters, which

accept TTL or CMOS inputs and output the

RS-232 signals with an inverted sense relative to

the input logic levels. Typically the RS-232 output

voltage swing is

±9V. Even under worst case

loading conditions of 3kOhms and 2500pF, the

output is guaranteed to be

±5V,whichisconsistent

with the RS-232 standard specifications. The

transmitter outputs are protected against infinite

short-circuits to ground without degradation in

reliability.

The instantaneous slew rate of the transmitter

output is internally limited to a maximum of 30V/

µs in order to meet the standards [EIA RS-232-D

2.1.7, Paragraph (5)]. However, the transition

region slew rate of these enhanced products is

typically 10V/

µs. The smooth transition of the

loaded output from V

monotonicity requirements of the standard [EIA

RS-232-D 2.1.7, Paragraphs (1) & (2)].