9

Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (50)668-707 • www.exar.com

SP3223E/EB/EU_0_06272

DESCRIPTION

The

SP3223 is a 2-driver/2-receiver device

ideal for portable or handheld applications.

The

SP3223 transceiversmeettheEIA/TIA-

232 and ITU-T V.28/V.24 communication

protocolsandcanbeimplementedinbattery-

powered, portable, or handheld applications

such as notebook or handheld computers.

The

SP3223 devices feature Exar's propri-

etary on-board charge pump circuitry that

generates ±5.5V RS-232 voltage levels from

a single +3.0V to +5.5V power supply.

These devices are an ideal choice for power

circuitry,the

SP3223reducesthepowersup-

ply drain to a µA supply current. In many

portableorhandheldapplications,anRS-232

cable can be disconnected or a connected

peripheral can be turned off. Under these

conditions, the internal charge pump and

the drivers will be shut down. Otherwise, the

system automatically comes online. This

feature allows design engineers to address

powersavingconcernswithoutmajordesign

changes.

THEORY OF OPERATION

The

SP3223 series is made up of four basic

circuit blocks:

. Drivers, 2. Receivers, 3. The Exar pro-

prietary charge pump, and 4. AUTO ON-

Drivers

The drivers are inverting level transmitters

thatconvertTTLorCMOSlogiclevelsto5.0V

EIA/TIA-232 levels with an inverted sense

relativetotheinputlogiclevels. Typically,the

RS-232 output voltage swing is +5.4V with

no load and +5V minimum fully loaded. The

driver outputs are protected against infinite

short-circuits to ground without degrada-

tion in reliability. These drivers comply with

the EIA-TIA-232F and all previous RS-232

versions. Unused driver inputs should be

connected to GND or V

The drivers can guarantee output data

rates fully loaded with 3kΩ in parallel with

000pF, (SP3223EU, C

compatibility with PC-to-PC communication

software.

The slew rate of the driver output on the

E and EB versions is internally limited to a

maximum of 30V/µs in order to meet the EIA

standards(EIARS-232D2..7,Paragraph5).

The Slew Rate of EU version is not limited

to enable higher speed data transfers. The

transition of the loaded output from HIGH to

LOW also meets the monotonicity require-

ments of the standard.

Figure 4 shows a loopback test circuit used

to test the RS-232 Drivers. Figure 15 shows

the test results where one driver was active

at 250kbps and all drivers are loaded with

an RS-232 receiver in parallel with a 000pF

capacitor. RS-232 data transmission rate of

20kbpsto Mbps providecompatibilitywith

designs in personal computer peripherals

and LAN applications.

Figure 3. Interface Circuitry Controlled by Micropro-

cessor Supervisory Circuit

SP3223E

2

4

6

5

3

7

19

5KΩ

5KΩ

GND

C1+

C1-

C2+

C2-

V+

V-

11

12

15

10

0.1µF

+

C2

C5

C1

+

+

C3

C4

+

+

17

8

16

9

RS-232

OUTPUTS

RS-232

INPUTS

14

20

11

18

R

R

T

T

T

R

R

ONLINE

SHUTDOWN

STATUS

UART

or

Serial µC

µP

Supervisor

IC

TTL/CMOS INPUTS

V

IN

RESET

0.1µF

0.1µF

0.1µF

0.1µF

T

EN

TTL/CMOS OUTPUTS