SP301 Datasheet, PDF(5/18 Page) Sipex Corporation – RS-232/RS-422 Line Drivers/Receivers

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SP301 Datasheet, PDF (5/18 Pages) Sipex Corporation – RS-232/RS-422 Line Drivers/Receivers

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VDD

VCC

3.3kâ¦

SP301/302

3.3kâ¦

2N2222

GND

VEE

VDD

VCC

3.3kâ¦

SP301/302

GND

VEE

VDD

VCC

SP301/302

3.3kâ¦

GND

VEE

2N2222

Figure 1. Isolating SP301/302 From Ground;

a) Single SP301/302; b) Multiple SP301/302

SOIC packages for operation over the commercial

temperature range.

circuitry. If the potential exists for momentary

shorts to voltages greater than Â±20V, it is recom-

mended that a 220â¦ resistor be wired in series

with each driver output. This will limit any

damage from the higher short-circuit current

from these higher voltage potentials. Voltage

clamps such as back-to-back Zener diodes can

be used to clamp the driver outputs to âsafeâ

levels. Short circuit current to ground is inter-

nally limited, and can therefore be sustained

infinitely. Under normal operating conditions,

the drivers can typically source 7mA at Â±5V

output, which exceeds the minimum RS-232

standards requirement.

If an SP301/302 transmitter output occupies a

data transmission line with other RS-232 de-

vices which are not powered by the same power

supplies, it is possible that a device that is not

powered will have a low impedance path to

ground at its driver output. The RS-232 stan-

dards require that with no power applied to the

device, the impedance from a transmitter output

to ground must be greater than 300â¦. This can

be easily achieved as shown in Figure 1a, where

an external transistor is used as a switch to

USING THE SP301/302

POWER SUPPLIES

The SP301/SP302 require Â±12V and +5V for

full RS-232 and RS-422 operation. The Â±12V

supplies set up the RS-232 Â±9V voltage swings,

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

formats the communications mode and controls

the loopback function. The supply voltages can

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

and 4.0V for VCC. Under these supply condi-

tions, derated performance can be expected.

POWER SUPPLY SEQUENCING

There are two requirements for power supply

sequencing for the SP301/302. The first is that

VDD is always greater than VCC. The second is

that when the part is powered up, VDD must be

applied 20ms before VCC.

GENERAL USAGE

RS232 Operation

The SP301 and SP302 are fully compliant

RS-232 devices. Their outputs are fully pro-

tected against shorts to Â±20V with no external

VDD

3.3kâ¦

2N2222

TIB1

VDD

VCC

VEE

GND

SP302

VCC

VEE

SELECT A = 1

SELECT B = 0

LOOPBACK = 1

TOB1

TIB2

TIA1

ROB1

TOB2

TOA1

TOA2

RIB1

ROB2

ROA1

RIB2

RIA1

RIA2

Figure 2. Typical Circuit

Corporation

SIGNAL PROCESSING EXCELLENCE

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