SP3238E Datasheet, PDF (9/20 Pages) Sipex Corporation – Intelligent +3.0V to +5.5V RS-232 Transceivers

The SP3238E drivers can maintain high data
rates up to 250kbps fully loaded. Figure 7 shows
a loopback test circuit used to test the RS-232
Drivers. Figure 8 shows the test results of the
loopback circuit with all three drivers active at
120kbps with typical RS-232 loads in parallel with
1000pF capacitors. Figure 9 shows the test results
where one driver was active at 250kbps and all
three drivers loaded with an RS-232 receiver in
parallel with a 1000pF capacitor. A solid RS-232
data transmission rate of 120kbps provides
compatibility with many designs in personal
computer peripherals and LAN applications.
Receivers
The receivers convert ±5.0V EIA/TIA-232
levels to TTL or CMOS logic output levels. All
receivers have an inverting output that can be
disabled by using the EN pin.
Receivers are active when the Auto-Online
circuitry is enabled or when in shutdown.
During the shutdown, the receivers will continue
to be active. If there is no activity present at the
receivers for a period longer than 100µs or when
SHUTDOWN is enabled, the device goes into a
standby mode where the circuit draws 1µA.
The truth table logic of the driver and receiver
outputs can be found in Table 2.
VCC
+
C5 0.1µF
VCC
C1+
+
V+
C1 0.1µF
C1-
C2+ SP3238E _V-
+
C2 0.1µF
C2-
LOGIC
INPUTS
TxIN
TxOUT
LOGIC
OUTPUTS
VCC
RxOUT
ONLINE
SHUTDOWN
RxIN
5kΩ
GND
+
C3 0.1µF
C4 0.1µF
+
1000pF
Figure 7. Loopback Test Circuit for RS-232 Driver Data
Transmission Rates
The SP3238E includes an additional non-
inverting receiver with an output R₁OUT. R₁OUT
is an extra output that remains active and monitors
activity while the other receiver outputs are
forced into high impedance. This allows Ring
Indicator (RI) from a peripheral to be monitored
without forward biasing the TTL/CMOS inputs
of the other devices connected to the receiver
outputs.
TBD
TBD
Figure 8. Loopback Test Circuit Result at 120kbps
(All Drivers Fully Loaded)
Figure 9. Loopback Test Circuit result at 235kbps
(All Drivers Fully Loaded)
SP3238EDS/04
SP3238E +3.0V to +5.5V RS-232 Transceivers
9
© Copyright 1999 Sipex Corporation