SP3222EEA-L-TR Datasheet, PDF (9/24 Pages) Exar Corporation – True +3.0V to +5.5V RS-232 Transceivers

VCC
+
C5 0.1µF
+
C1 0.1µF
+
C2 0.1µF
LOGIC
INPUTS
VCC
C1+
V+
C1-
C2+ ^SP3222E V-
SP3232E
C2-
TxIN
TxOUT
+
C3 0.1µF
C4 0.1µF
+
LOGIC
OUTPUTS
RxOUT
EN*
RxIN
5kΩ
*SHDN
VCC
GND
1000pF
* SP3222E only
Figure 8. SP3222E/SP3232E Driver Loopback Test
Circuit
[
T
]
T1 IN 1
T
T1 OUT 2
T
T
R1 OUT 3
Ch1 5.00V Ch2 5.00V M 5.00µs Ch1 0V
Ch3 5.00V
Figure 9. Loopback Test results at 120kbps
T1 IN 1
[
T
]
T
T1 OUT 2
T
T
R1 OUT 3
Ch1 5.00V Ch2 5.00V M 2.50µs Ch1 0V
Ch3 5.00V
DESCRIPTION
Receivers
The Receivers convert EIA/TIA-232 levels
to TTL or CMOS logic output levels. The
SP3222E 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 SP3222E
driver and receiver outputs can be found in
Table 2.
SHDN
EN
TxOUT
RxOUT
0
0
Tri-state
Active
0
1
Tri-state
Tri-state
1
0
Active
Active
1
1
Active
Tri-state
Table 2. SP3222E Truth Table Logic for Shutdown
and Enable Control
Since receiver input is usually from a trans-
mission line where long cable lengths and
system interference can degrade the signal,
the inputs have a typical hysteresis margin
of 300mV. This ensures that the receiver
is virtually immune to noisy transmission
lines. Should an input be left unconnected,
an internal 5kΩ pulldown resistor to ground
will commit the output of the receiver to a
HIGH state.
Charge Pump
The charge pump is an Exar-patended
design (U.S. 5,306,954) and uses a unique
approach compared to older less-efficient
designs. The charge pump still requires four
external capacitors, but uses a four-phase
voltage shifting technique to attain sym-
metrical 5.5V power supplies. The internal
power supply consists of a regulated dual
charge pump that provides output voltages
of +/-5.5V regardless of the input voltage
(Vcc) over the +3.0V to +5.5V range.
Figure 10. Loopback Test results at 235kbps
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

SP3222E/SP3232E_101_031413