SP3220EUEY-L-TR Datasheet, PDF (10/20 Pages) Exar Corporation – 3.0V to +5.5V RS-232 Driver/Receiver Pair

VCC
+
C5 0.1µF
C1 ⁺ 0.1µF
+
C2 0.1µF
LOGIC
INPUTS
VCC
C1+
V+
C1-
C2+ SP3220
V-
E/EB/EU
C2-
TxIN
TxOUT
+
C3 0.1µF
C4 0.1µF
+
LOGIC
OUTPUTS
RxOUT
RxIN
5kΩ
EN
*SHDN
VCC
GND
(SP3220EU 250pF)
(SP3220E/EB 1000pF)
Figure 12. SP3220E/EB/EU Driver Loopback Test
Circuit
DESCRIPTION
(tri-stated) and the charge pump is turned
off with V+ pulled down to Vcc and V- pulled
to GND. The time required to exit shutdown
is typically 100ms. Connect SHDN to Vcc if
the shutdown mode is not used. SHDN has
no effect on RxOUT. Note that the driver is
enabled only when the magnitude of V- ex-
ceeds approximately 3V.
Receiver
The receiver converts EIA/TIA-232 levels
to TTL or CMOS logic output levels. The
receiver has an inverting high-impedance
output. This receiver output (RxOUT) is at
high-impedance when the enable control
EN = HIGH. In the shutdown mode, the
receiver can be active or inactive. EN has
no effect on TxOUT. The truth table logic
of the SP3220E/EB/EU driver and receiver
outputs can be found in Table 2.
Figure 13. SP3220EB Loopback Test results at
250kbps
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. SP3220E/EB/EU 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 pull-down resistor to ground
will commit the output of the receiver to a
HIGH state.
Figure 14. SP3220EU Loopback Test results at
1Mbps
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
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SP3220E_EB_EU_102_102016