SP3220E datasheet(8/18 Pages) SIPEX

8 / 18 page

11/07/02

SP3220E True +3.0 to +5.0V RS-232 Transceivers

DESCRIPTION

The SP3220E device meets the EIA/TIA-232

and V.28/V.24 communication protocols and

can be implemented in battery-powered,

portable, or hand-held applications such as

notebook or palmtop computers. The SP3220E

device features Sipex's proprietary on-board

charge pump circuitry that generates 2 x V

CC for

RS-232 voltage levels from a single +3.0V to

+5.5V power supply. This series is ideal for

+3.3V-only systems, mixed +3.0V to +5.5V

systems, or +5.0V-only systems that require true

RS-232 performance. The SP3220E device has

a driver that operates at a typical data rate of

235Kbps fully loaded.

The SP3220E is a 1-driver/1-receiver device

ideal for portable or hand-held applications.

The SP3220E features a 1

µA shutdown mode

that reduces power consumption and extends

battery life in portable systems. Its receivers

remain active in shutdown mode, allowing

external devices such as modems to be

monitored using only 1

µA supply current.

THEORY OF OPERATION

The SP3220E device is made up of three basic

circuit blocks: 1. Drivers, 2. Receivers, and 3.

the Sipex proprietary charge pump.

Drivers

The drivers are inverting level transmitters that

convert TTL or CMOS logic levels to +5.0V

EIA/TIA-232 levels inverted relative to the

input logic levels. Typically, the RS-232 output

voltage swing is +5.5V with no load and at least

+5V minimum fully loaded. The driver outputs

are protected against infinite short-circuits to

ground without degradation in reliability. Driver

outputs will meet EIA/TIA-562 levels of +3.7V

with supply voltages as low as 2.7V.

The drivers typically can operate at a data rate

of 235Kbps. The drivers can guarantee a data

rate of 120Kbps fully loaded with 3K

Ω in

parallel with 1000pF, ensuring compatibility

with PC-to-PC communication 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.

The SP3220E driver can maintain high data

rates up to 235Kbps fully loaded. Figure 6 shows

a loopback test circuit used to test the

RS-232 driver. Figure 7 shows the test results of

the loopback circuit with the driver active at

120Kbps with an RS-232 load in parallel with a

1000pF capacitor. Figure 8 shows the test results

where the driver was active at 235Kbps and

loaded with an RS-232 receiver in parallel with

a 1000pF capacitor. A solid RS-232 data

transmission rate of 120Kbps provides

compatibility with many designs in personal

computer peripherals and LAN applications.

The SP3220E driver's output stage is turned off

(high-Z) when the device is in shutdown mode.

When the power is off, the SP3220E device

permits the outputs to be driven up to +12V. The

driver's input does not have pull-up resistors.

Designers should connect an unused input

to V

CC or GND.

In the shutdown mode, the supply current falls to

less than 1

µA, where SHDN = LOW. When the

SP3220E device is shut down, the device's

driver output is disabled (high-Z) and the charge

pump is turned off with V+ pulled down to V

and V- pulled to GND. The time required to exit

shutdown is typically 100

µs. Connect SHDN to

CC if the shutdown mode is not used. SHDN has

no effect on RxOUT. Note that the driver is

enabled only when the magnitude of V- exceeds

approximately 3V.

SP3220E Datasheet(PDF) 8 Page - Sipex Corporation

SP3220E Datasheet(HTML) 8 Page - Sipex Corporation

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