SP3222EEA-L-TR Datasheet, PDF (8/24 Pages) Exar Corporation – True +3.0V to +5.5V RS-232 Transceivers

The SP3222E/SP3232E transceivers
meet the EIA/TIA-232 and ITU-T V.28/V.24
communication protocols and can be imple-
mented in battery-powered, portable, or
hand-held applications such as notebook or
palmtop computers. The SP3222E/SP3232E
devices feature Exar's proprietary on-board
charge pump circuitry that generates ±5.5V
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. The
SP3222E/SP3232E devices can operate
at a typical data rate of 235kbps when fully
loaded.
The SP3222E and SP3232E are 2-driver/2-
receiver devices ideal for portable or hand-
held applications. The SP3222E features a
1µA shutdown mode that reduces power
consumption and extends battery life in por-
table systems. Its receivers remain active in
shutdown mode, allowing external devices
such as modems to be monitored using only
1µA supply current.
DESCRIPTION
The drivers can guarantee a data rate of
120kbps fully loaded with 3kΩ in parallel
with 1000pF, ensuring compatability with
PC-to-PC communication software.
The slew rate of the driver is internally limited
to a maximum of 30V/µs in order to meet the
EIA standards (EIA RS-232D 2.1.7, Para-
graph 5). The transition of the loaded output
from HIGH to LOW also meet the monotonic-
ity requirements of the standard.
Figure 8 shows a loopback test circuit
used to test the RS-232 Drivers. Figure
9 shows the test results of the loopback
circuit with all drivers active at 120kbps
with RS-232 loads in parallel with a
1000pF capacitor. Figure 10 shows the
test results where one driver was active
at 235kbps and all drivers loaded with an
RS-232 receiver in parallel with 1000pF
capacitors. A solid RS-232 data transmis-
sion rate of 120kbps provides compatibility
with many designs in personal computer
peripherals and LAN applications.
THEORY OF OPERATION
The SP3222E/SP3232E series is made up
of three basic circuit blocks:
1. Drivers
2. Receivers
3. The Exar proprietary charge pump
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 with-
out degradation in reliability. Driver outputs
will meet EIA/TIA-562 levels of +/-3.7V with
supply voltages as low as 2.7V.
The SP3222E driver's output stages are
turned off (tri-state) when the device is in
shutdown mode. When the power is off, the
SP3222E device permits the outputs to be
driven up to +/-12V. The driver's inputs do
not have pull-up resistors. Designers should
connect unused inputs to Vcc or GND.
In the shutdown mode, the supply current
falls to less than 1µA, where SHDN = LOW.
When the SP3222E 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.
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

SP3222E/SP3232E_101_031413