SP3223EBCASLASHTR datasheet(10/25 Pages) SIPEX

10 / 25 page

Date: 6/2/04

SP3223EB/3243EB +3.0V to +5.5V RS-232 Transceivers

DESCRIPTION

The SP3223EB and SP3243EB transceivers meet

the EIA/TIA-232 and ITU-T V.28/V.24 com-

munication protocols and can be implemented

in battery-powered, portable, or hand-held ap-

plications such as notebook or palmtop comput-

ers. The SP3223EB and SP3243EB devices

feature Sipex's proprietary and patented (U.S.--

5,306,954) on-board charge pump circuitry that

generates

±5.5V RS-232 voltage levels from a

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

SP3223EB and SP3243EB devices can operate

at a data rate of 250kbps fully loaded.

The SP3223EB is a 2-driver/2-receiver device,

and the SP3243EB is a 3-driver/5-receiver de-

vice ideal for portable or hand-held applications.

The SP3243EB includes one complementary

always-active receiver that can monitor an

external device (such as a modem) in shutdown.

This aids in protecting the UART or serial

controller IC by preventing forward biasing

of the protection diodes where VCC may be

disconnected.

The SP3223EB and SP3243EB series is an ideal

choice for power sensitive designs. The

SP3223EB and SP3243EB devices feature

AUTO ON-LINE® circuitry which reduces the

power supply drain to a 1

µA supply current. In

many portable or hand-held applications, an RS-

232 cable can be disconnected or a connected

peripheral can be turned off. Under these condi-

tions, the internal charge pump and the drivers

will be shut down. Otherwise, the system auto-

matically comes online. This feature allows de-

sign engineers to address power saving concerns

without major design changes.

THEORY OF OPERATION

The SP3223EB and SP3243EB series is made up

of four basic circuit blocks:

1. Drivers,

2. Receivers,

3. the Sipex proprietary charge pump, and

4. AUTO ON-LINE® circuitry.

Drivers

The drivers are inverting level transmitters that

convert TTL or CMOS logic levels to 5.0V EIA/

TIA-232 levels with an inverted sense relative to

the input logic levels. 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 degradation 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 VCC.

The drivers can guarantee a data rate of 250kbps

fully loaded with 3k

Ω in parallel with 1000pF,

ensuring compatibility with PC-to-PC commu-

nication software.

The slew rate of the driver output is internally

limited to a maximum of 30V/

µs in order to

meet the EIA standards (EIA RS-232D 2.1.7,

Paragraph 5). The transition of the loaded

output from HIGH to LOW also meets the

monotonicity requirements of the standard.

Figure 16. Interface Circuitry Controlled by Micropro-

cessor Supervisory Circuit

SP3243EB

5KΩ

GND

C1+

C1-

C2+

C2-

V+

V-

VCC

0.1µF

RS-232

OUTPUTS

RS-232

INPUTS

VCC

1IN

1OUT

1IN

2OUT

2IN

3IN

3OUT

1OUT

2IN

3IN

4IN

5IN

2OUT

3OUT

4OUT

5OUT

ONLINE

SHUTDOWN

STATUS

UART

Serial C

Supervisor

TxD

RTS

DTR

RxD

CTS

DSR

DCD

VCC

VIN

RESET

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