DESCRIPTION
Thedriverscanguaranteeadatarateof 250kbps
fully loaded with 3KΩ in parallel with 1000pF,
ensuring compatibility with PC-to-PC commu-
nication software.
The SP3222EB/3232EB transceivers meet 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
SP3222EB/3232EB devices all feature Sipex's
proprietary on-board charge pump circuitry that
generates 2 x VCC 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 +3.3V to +5.5V systems, or +5.0V-only
systems that require true RS-232 performance.
TheSP3222EB/3232EBserieshavedriversthat
operate at a typical data rate of 250kbps fully
loaded.
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 10 shows a loopback test circuit used to
the RS-232 drivers. Figure 11 shows the test
results of the loopback circuit with all drivers
active at 120kbps with RS-232 loads in parallel
with 1000pF capacitors. Figure 12 shows the
test results where one driver was active at
250kbps and all drivers loaded 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 appli-
cations.
The SP3222EB and SP3232EB are 2-driver/2-
receiver devices ideal for portable or hand-held
applications. The SP3222EB features a 1µA
shutdown mode that reduces power consump-
tionandextendsbatterylifeinportablesystems.
Its receivers remain active in shutdown mode,
allowing external devices such as modems to be
monitored using only 1µA supply current.
The SP3222EB driver'soutputstagesareturned
off (tri-state) when the device is in shutdown
mode. When the power is off, the SP3222EB
device permits the outputs to be driven up to
±12V. The driver's inputs do not have pull-up
resistors. Designers should connect unused in-
puts to VCC or GND.
THEORY OF OPERATION
The SP3222EB/3232EB series are made up of
three basic circuit blocks: 1. Drivers, 2.
Receivers, and 3. the Sipex proprietary charge
pump.
In the shutdown mode, the supply current falls
to less than 1µA, where SHDN = LOW. When
the SP3222EB device is shut down, the device's
driver outputs are disabled (tri-stated) and the
charge pumps are turned off with V+ pulled
down to VCC and V- pulled to GND. The time
required to exit shutdown is typically 100µs.
Connect SHDN to VCC if the shutdown mode is
not used.
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 in-
put 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
groundwithoutdegradationinreliability. Driver
outputs will meet EIA/TIA-562 levels of ±3.7V
with supply voltages as low as 2.7V.
Rev. A Date:12/11/03
SP3222EB/3232EB True +3.0 to +5.5V RS-232 Transceivers
© Copyright 2003 Sipex Corporation
8
SIPEX [ SIPEX CORPORATION ]
