SP3238EE Datasheet, PDF (9/20 Pages) Sipex Corporation – Intelligent +3.0V to +5.5V RS-232 Transceiver

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 five driv-
ers active at 120kbps with typical RS-232 loads
in parallel with 1000pF capacitors. Figure 6 shows
the test results where one driver was active at
250kbps and all five 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 appli-
cations.
Receivers
The receivers convert ±5.0V EIA/TIA-232
levels to TTL or CMOS logic output levels.
Receivers are not active when in shutdown. If
there is no activity present at the receivers for a
period longer than 100µs during AUTO ON-
LINE^® mode 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.
The SP3238EE 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
VCC
+
C5 0.1µF
+
C1 0.1µF
+
C2 0.1µF
VCC
C1+
V+
C1-
C2+ SP3238EE _V-
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
Indicator (RI) from a peripheral to be monitored
without forward biasing the TTL/CMOS inputs
of the other devices connected to the receiver
outputs.
Since receiver input is usually from a transmission
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
Figure 8. Loopback Test Circuit Result at 120kbps
(All Drivers Fully Loaded)
Figure 9. Loopback Test Circuit result at 250kbps
(All Drivers Fully Loaded)
Date: 02/24/05
SP3238EE Intelligent +3.0V to +5.5V RS-232 Transceiver
9
© Copyright 2005 Sipex Corporation