SP3221E Datasheet, PDF (7/18 Pages) Sipex Corporation – Intelligent +3.0V to +5.5V RS-232 Transceiver

DESCRIPTION
The SP3221E transceiver meets the EIA/
TIA-232 and ITU-T V.28/V.24 communication
protocols and can be implemented in battery-
powered, portable, or hand-held applications
such as notebook or hand held computers. The
SP3221E device features 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 SP3221E device can operate
at a typical data rate of 240Kbps fully loaded.
The SP3221E is a 1-driver/1-receiver device is
ideal for portable or hand-held applications and
power sensitive designs. The device features
Auto-Online circuitry which reduces the power
supply drain to a 1µA supply current. In many
portable or hand-held applications, an RS-232
cable can be disconnected when not in use.
Under these conditions, the internal charge pump
and the driver will be shut down. Otherwise, the
device automatically comes online. This feature
allows design engineers to address power saving
concerns without major design changes.
THEORY OF OPERATION
The SP3221E device is made up of four basic
circuit blocks: 1. Drivers, 2. Receivers,
3. the Sipex proprietary charge pump, and
4. Auto-Online circuitry.
Drivers
The driver is 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. This
driver complies with the EIA-TIA-232F and all
previous RS-232 versions.
The driver typically can operate at a data rate
of 250Kbps. The driver can guarantee a data rate
of 250Kbps fully loaded with 3KΩ 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 SP3221E driver can maintain high data
rates up to 240Kbps fully loaded. Figure 6
shows a loopback test circuit used to test the
RS-232 drivers. Figure 7 shows the test results
of the loopback circuit with the driver active at
250Kbps with typical RS-232 loads in parallel
with 1000pF capacitors. Figure 8 shows the test
results where the loaded driver was active at
235Kbps with an RS-232 receiver in parallel
with a 1000pF capacitor. A solid RS-232 data
transmission rate of 250Kbps provides
compatibility with many designs in personal
computer peripherals and LAN applications.
Date: 7/21/04
SP3221E +3.0V to +5.5V RS-232 Transceiver
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© Copyright 2004 Sipex Corporation