SP3222EU Datasheet, PDF (8/20 Pages) Sipex Corporation – 3.3V, 1000 Kbps RS-232 Transceivers

The SP3222EU/SP3232EU 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 SP3222EU/
SP3232EU devices feature Exar's propri-
etary 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 SP3222EU/SP3232EU
devices can operate at a minimum data rate
of 1000kbps.
The SP3222EU and SP3232EU are 2-
driver/2- receiver devices ideal for portable
or hand-held applications. The SP3222EU
features a 1µA 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 1µA supply current.
THEORY OF OPERATION
The SP3222EU/SP3232EU series is made
up of three basic circuit blocks:
1. Drivers
2. Receivers
3. The Exar proprietary charge pump
DESCRIPTION
The drivers have a minimum data rate of
1000kbps fully loaded with 3kΩ in parallel
with 250pF, ensuring compatability with PC-
to-PC communication software.
Figure 11 shows a loopback test circuit
used to test the RS-232 Drivers. Figure
12 shows the test results of the loopback
circuit with all drivers active at 250kbps
with RS-232 loads in parallel with a
1000pF capacitor. Figure 13 shows the
test results where one driver was active
at 1000kbps and all drivers loaded with an
RS-232 receiver in parallel with 250pF
capacitors.
The SP3222EU driver's output stages are
turned off (tri-state) when the device is in
shutdown mode. When the power is off, the
SP3222EU 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 SP3222EU 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.
Receivers
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 Receivers convert EIA/TIA-232 levels
to TTL or CMOS logic output levels. The
SP3222EU receivers have an inverting
tri-state output. These receiver outputs
(RxOUT) are tri-stated when the enable
control EN = HIGH. In the shutdown mode,
the receivers can be active or inactive. EN
has no effect on TxOUT. The truth table logic
of the SP3222EU driver and receiver outputs
can be found in Table 2.
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

SP3222EU/SP3232EU_102_031413