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SP3243EBCA-L-TR Datasheet, PDF (9/25 Pages) Exar Corporation – 3 Driver/5 Receiver Intelligent +3.0V to +5.5V RS-232 Transceivers | |||
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+3V to +5V
+
C5 0.1 µF
+
C1 0.1 µF
+
C2 0.1 µF
TTL/CMOS
INPUTS
C1+
C1-
C2+
C2-
T1IN
TXIN
VCC
V+
SP3243
V-
T1OUT
TXOUT
+
C3 0.1 µF
C4 0.1 µF
+
TTL/CMOS
OUTPUTS
VCC
To µP Supervisor
Circuit
R1OUT
R1IN
5Kâ¦
RXOUT
RXIN
5Kâ¦
1000pF
SHUTDOWN
ONLINE
STATUS
GND
18
1000pF
Figure 11. Loopback Test Circuit for RS-232 Driver
Data Transmission Rates
Device: SP3243E
SHUTDOWN TxOUT RxOUT
0
High-Z High-Z
1
Active
Active
R2OUT
Active
Active
Table 2. SHUTDOWN Truth Tables
Note: In AUTO ON-LINE® Mode where ONLINE = GND
and SHUTDOWN = VCC, the device will shut down if
there is no activity present at the Receiver inputs.
Receivers
The receivers convert +5.0V EIA/TIA-232
levels to TTL or CMOS logic output levels. Re-
ceivers are High-Z when the AUTO ON-LINE®
circuitry is enabled or when in shutdown. The
truth table logic of the SP3243 driver and receiver
outputs can be found in Table 2.
The SP3243E includes an additional non-in-
verting receiver with an output R2OUT. R2OUT
is an extra output that remains active and
monitors activity while the other receiver
outputs are forced into high impedance.
This allows a Ring Indicator (RI) signal from a
peripheral to be monitored without forward
biasing the TTL/CMOS inputs of the other
devices connected to the receiver outputs.
Figure 12. Loopback Test results at 1Mbps
Since receiver input is usually from a transmis-
sion 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 5K⦠pulldown resistor
to ground will commit the output of the receiver
to a HIGH state.
Figure 13. Loopback Test results at 250Kbps
Exar Corporation 48720 Kato Road, Fremont CA, 94538 ⢠510-668-7017 ⢠www.exar.com
SP3243E_102_060611
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