SP3243E EXAR [Exar Corporation], SP3243E Datasheet - Page 9

• Manufacturer Part Number: SP3243E
• Description: 3 Driver/5 Receiver Intelligent +3.0V to +5.5V RS-232 Transceivers
• Manufacturer: EXAR [Exar Corporation]

Figure 12. Loopback Test results at 1Mbps
Figure 11. Loopback Test Circuit for RS-232 Driver
Data Transmission Rates
Figure 13. Loopback Test results at 250Kbps
To µP Supervisor
Circuit
TTL/CMOS
TTL/CMOS
OUTPUTS
INPUTS
C2
C5
C1
V
CC
+
+
+
0.1 µF
0.1 µF
0.1 µF
C1+
C1-
R
C2+
C2-
T
R
SHUTDOWN
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
T
ONLINE
STATUS
1
X
1
X
IN
OUT
IN
OUT
SP3243
+3V to +5V
V
GND
CC
18
5KΩ
5KΩ
T
T
1
X
R
R
OUT
OUT
1
X
V+
IN
IN
V-
1000pF
C3
C4
+
+
0.1 µF
0.1 µF
1000pF
9
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 R
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.
Table 2. SHUTDOWN Truth Tables
Note: In AUTO ON-LINE
and SHUTDOWN = V
there is no activity present at the Receiver inputs.
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 5KΩ pulldown resistor
to ground will commit the output of the receiver
to a HIGH state.
Device: SP3243E
SHUTDOWN
0
1
TxOUT
High-Z
Active
CC
®
, the device will shut down if
Mode where ONLINE = GND
RxOUT
High-Z
Active
SP3243E_100_072309
2
OUT. R
R2OUT
Active
Active
2
OUT
®