SP3220EBCY-L Datasheet, PDF (9/19 Pages) Sipex Corporation – High Speed +3.0V to +5.5V RS-232 Driver/Receiver Pair

DESCRIPTION
The SP3220EB/EU 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 SP3220EB/
EU 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 re-
quire true RS-232 performance. The SP3220EB
device has a driver that can operate at a data rate
of 250Kbps fully loaded. The SP3220EU can
Operate at 1000Kbps
The SP3220EB/EU is a 1-driver/1-receiver de-
vice ideal for portable or hand-held applications.
The SP3220EB/EU features a 1µA shutdown
mode that reduces power consumption and ex-
tends battery life in portable systems. Its receiv-
ers remain active in shutdown mode, allowing
external devices such as modems to be
monitored using only 1µA supply current.
THEORY OF OPERATION
The SP3220EB/EU 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 SP3220EU drivers can guarantee a data rate
of 1000Kbps fully loaded with 3 in parallel
with 250pF.
The slew rate of the SP3220EB output is inter-
nally 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 12 shows a loopback circuit used to test
the RS-232 driver. Figure 13 shows the test
results of the loopback circuit with the SP3220EB
driver active at 250Kbps with an RS-232 load in
parallel with a 1000pF capacitor. Figure 14
shows the test results where the SP3220EU
driver was active at 1000Kbps and loaded with
an RS-232 receiver in parallel with a 250pF
capacitor. A solid RS-232 data transmission rate
of 250Kbps provides compatibility with many
designs in personal computer peripherals and
LAN applications.
The SP3220EB/EU driver's output stage is turned
off (high-Z) when the device is in shutdown
mode. When the power is off, the SP3220EB/
EU 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 1µA, where SHDN = LOW. When the
SP3220EB/EU 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_CC
and V- pulled to GND. The time required to exit
shutdown is typically 100µs. Connect SHDN to
V if the shutdown mode is not used. SHDN has
CC
no effect on RxOUT. Note that the driver is
enabled only when the magnitude of V- exceeds
approximately 3V.
The SP3220EB drivers typically can operate at
a data rate of 250Kbps fully loaded with 3KΩ in
parallel with 1000pF, ensuring compatibility
with PC-to-PC communication software.
Rev: A Date:12/11/03
SP3220EB/EU +3.0 to +5.0V RS-232 Transceivers
9
© Copyright 2002 Sipex Corporation