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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP207E_100_072309
FEATURES
The SP207E, SP208E, SP211E and
SP213E multi–channeltransceiverstmost
RS-232/V.28communicationneeds.Allof
thesedevicesfeaturelow–powerCMOScon-
struction and EXAR–proprietary on-board
charge pump circuitry to generate RS-232
signal-voltages, making them ideal for appli-
cations where +9V and -9V supplies are not
available.Thehighlyefcientchargepump
is optimized to use small and inexpensive
0.1µF charge pump capacitors, saving board
space and reducing overall circuit cost.
Each device provides a different driver/
receiver combination to match standard
application requirements. The SP207E is
a 5-driver, 3-receiver device, ideal for DCE
applications such as modems, printers or
other peripherals. SP208Eisa4-driver/4-
receiver device, ideal for providing hand-
shaking signals in V.35 applications or other
general-purpose serial communications.
The SP211E and SP213E are each 3-driver,
5-receiver devices ideal for DTE serial ports
on a PC or other data-terminal equipment.
The SP211E and SP213E feature a low–
power shutdown mode, which reduces power
supply drain to 1µA. The SP213E includes a
Wake-Upfunctionwhichkeepstworeceivers
active in the shutdown mode, unless disabled
by the EN pin.
Thefamilyisavailablein28and24pinSO
(wide)andSSOP(shrink)smalloutlinepack-
ages.Devicescanbespeciedforcommer-
cial(0˚Cto+70˚C)andindustrial/extended
(–40˚Cto+85˚C)operatingtemperatures.
THEORY OF OPERATION
Exar RS-232 transceivers contain three
basiccircuitblocks—a)transmitter/driver,
b) receiver and c) the EXAR–proprietary
charge pump. SP211E and SP213E also
include SHUTDOWN and ENABLE func-
tions.
Transmitter/Drivers
The drivers are single-ended inverting trans-
mitters,whichaccepteitherTTLorCMOS
inputs and output the RS-232 signals with
an inverted sense relative to the input logic
levels. Should the input of the driver be left
open, an internal pullup to VCC forces the
input high, thus committing the output to a
logic-1 (MARK) state. The slew rate of the
transmitter output is internally limited to a
maximum of 30V/µs in order to meet the
EIA/RS-232andITUV.28standards.The
transition of the output from high to low also
meets the monotonicity requirements of the
standard even when loaded. Driver output
voltage swing is ±7V (typical) with no load,
and ±5V or greater at maximum load. The
transmitter outputs are protected against
innite short–circuits to ground without
degradation in reliability.
The drivers of the SP211E, and SP213E
canbetri–statedbyusingtheSHUTDOWN
function. In this “power-off” state the charge
pump is turned off and VCC current drops to
1µA typical. Driver output impedance will
remain greater than 300Ω, satisfying the
RS-232andV.28specications.ForSP211E
SHUTDOWNisactivewhenpin25isdriven
high. For SP213ESHUTDOWNisactive
when pin 25 is driven low.
Receivers
The receivers convert RS-232 level input
signals to inverted TTL level signals. Because
signals are often received from a transmis-
sion line where long cables and system
interference can degrade signal quality, the
inputs have enhanced sensitivity to detect
weakened signals. The receivers also fea-
ture a typical hysteresis margin of 500mV for
clean reception of slowly transitioning signals
in noisy conditions. These enhancements
ensure that the receiver is virtually immune
to noisy transmission lines.