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Exar Corporation 48720 Kato Road, Fremont CA, 94538 50-668-707 www.exar.com
SP2EH_23EH_0_060
FEATuRES
As in the original RS-232 multi-channel
products, the
SP211EH and SP213EH high
speed multi–channel RS-232 line transceiv-
ersprovideavarietyofconfigurationstofit
most designs, especially high speed appli-
cations where +/-2V is not available. The
SP211EH/213EH is a superior high speed
drop-inreplacementtoourpreviousversions
as well as popular industry standards.
All devices in this series feature low–power
CMOS construction and
Exar's–proprietary
on-board charge pump circuitry to generate
the RS-232 signal voltages. The ability to
use 0.F charge pump capacitors saves
board space and reduces production costs.
The devices in this series provide different
driver/receiver combinations to match any
application requirement.
The
SP211EHandSP213EHmodels feature
alow–powershutdownmode,whichreduces
power supply drain to A. The
SP213EH
includesaWake-Upfunctionwhichkeeps
two receivers active in the shutdown mode,
unless disabled by the EN pin.
The family is available in 28 SOIC (wide)
and SSOP (shrink) small outline packages.
Devicescanbespecifiedforcommercial(0C
to+70C)andindustrial/extended(–40Cto
+85C)operatingtemperatures.
THEORY OF OPERATION
The
SP211EH and SP213EH devic-
es are made up of three basic cir-
cuit blocks — ) transmitter/driver,
2) receiver and 3) the
ExAR–proprietary
charge pump. Each model within the series
incorporates variations of these circuits to
achievethedesiredconfigurationandper-
formance.
Transmitter/Drivers
The drivers of this series can maintain a
typical data rate of 500kbps.
This superior RS-232 data transmission
rate makes the
SP211EH/213EH series an
ideal match for many designs in personal
computer peripherals and LAN applications
that demand high speed performance.
The drivers are inverting transmitters, which
accepteitherTTLorCMOSinputsandoutput
the RS-232 signals with an inverted sense
relativetotheinputlogiclevels. Typically,the
RS-232 output voltage swing is +/-9V with
no load, and +/-5V minimum with full load.
Thetransmitteroutputsareprotectedagainst
infinite short–circuits to ground without
degradation in reliability. The drivers of the
SP211EH, and SP213EH can be tri–stated
byusingtheSHUTDOWNfunction.
In the "power-off" state, the output imped-
ance will remain greater than 300 ohms,
againsatisfyingtheRS-232specifications.
Should the input of the driver be left open,
an internal 400k ohm pull-up resistor to VCC
forces the input high, thus committing the
output to a low state. The slew rate of the
transmitter output is internally limited to a
maximum of 30V/s 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.
Receivers
The high performance receivers of the
SP211EH/213EH devices can accept input
signals at a typical data rate or 500kbps.The
receivers convert RS-232 level input signals
to inverted TTL level signals. Since the input
isusuallyfromatransmissionlinewherelong
cable lengths and system interference can
degrade the signal, the inputs have a typical
hysteresis margin of 500mV. This ensures
transmission lines. Should an input be left
unconnected, a 5k pull-down resistor to
ground will commit the output of the receiver
to a high state.