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ICL232 Datasheet(PDF) 4 Page - Harris Corporation

Part No. ICL232
Description  5V Powered, Dual RS-232 Transmitter/Receiver
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Maker  HARRIS [Harris Corporation]
Homepage  http://www.harris.com
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ICL232 Datasheet(HTML) 4 Page - Harris Corporation

   
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Detailed Description
The ICL232 is a dual RS-232 transmitter/receiver powered by
a single +5V power supply which meets all ElA RS232C spec-
ifications and features low power consumption. The functional
diagram illustrates the major elements of the ICL232. The cir-
cuit is divided into three sections: a voltage doubler/inverter,
dual transmitters, and dual receivers Voltage Converter.
An equivalent circuit of the dual charge pump is illustrated in
Figure 5.
The voltage quadrupler contains two charge pumps which use
two phases of an internally generated clock to generate +10V
and -10V. The nominal clock frequency is 16kHz. During
phase one of the clock, capacitor C1 is charged to VCC.
During phase two, the voltage on C1 is added to VCC,
producing a signal across C2 equal to twice VCC. At the same
time, C3 is also charged to 2VCC, and then during phase one,
it is inverted with respect to ground to produce a signal across
C4 equal to -2VCC. The voltage converter accepts input
voltages up to 5.5V. The output impedance of the doubler (V+)
is approximately 200
Ω, and the output impedance of the
inverter (V-) is approximately 450
Ω . Typical graphs are
presented which show the voltage converters output vs input
voltage and output voltages vs load characteristics. The test
circuit (Figure 3) uses 1
µF capacitors for C1-C4, however, the
value is not critical. Increasing the values of C1 and C2 will
lower the output impedance of the voltage doubler and
inverter, and increasing the values of the reservoir capacitors,
C3 and C4, lowers the ripple on the V+ and V- supplies.
Transmitters
The transmitters are TTL/CMOS compatible inverters which
translate the inputs to RS-232 outputs. The input logic thresh-
old is about 26% of VCC , or 1.3V for VCC = 5V. A logic 1 at
the input results in a voltage of between -5V and V- at the out-
put, and a logic 0 results in a voltage between +5V and (V+
- 0.6V). Each transmitter input has an internal 400k
Ω pullup
resistor so any unused input can be left unconnected and its
output remains in its low state. The output voltage swing
meets the RS-232C specification of
±5V minimum with the
worst case conditions of: both transmitters driving 3k
Ω mini-
mum load impedance, VCC = 4.5V, and maximum allowable
operating temperature. The transmitters have an internally
limited output slew rate which is less than 30V/
µs. The outputs
are short circuit protected and can be shorted to ground indef-
initely. The powered down output impedance is a minimum of
300
Ω with ±2V applied to the outputs and VCC = 0V.
Receivers
The receiver inputs accept up to
±30V while presenting the
required 3k
Ω to 7kΩ input impedance even it the power is off
(VCC = 0V). The receivers have a typical input threshold of
1.3V which is within the
±3V limits, known as the transition
region, of the RS-232 specification. The receiver output is
0V to VCC. The output will be low whenever the input is
greater than 2.4V and high whenever the input is floating or
driven between +0.8V and -30V. The receivers feature 0.5V
hysteresis to improve noise rejection.
12
12
R1OUT
Receiver 1 TTL/CMOS output.
13
13
R1IN
RS-232 Receiver 1 input, with internal 5K pulldown resistor to GND.
14
14
T1OUT
RS-232 Transmitter 1 output
±10V (typical).
15
15
GND
Supply Ground.
16
16
VCC
Positive Power Supply +5V
±10%
Pin Descriptions (Continued)
PDIP, CERDIP
SOIC
PIN NAME
DESCRIPTION
+
-
C1
+
-
C3
+
-
C2
+
-
C4
S1
S2
S5
S6
S3
S4
S7
S8
VCC
GND
RC
OSCILLATOR
VCC
GND
V+ = 2VCC
GND
V- = -(V+)
C1+
C1
-
C2
-
C2+
VOLTAGE INVERTER
VOLTAGE DOUBLER
FIGURE 5. DUAL CHARGE PUMP
T1IN, T2IN
T1OUT, T2OUT
VOH
VOL
tr
tf
90%
10%
Instantaneous
Slew Rate (SR)
=
(0.8) (VOH - VOL)
tr
or
(0.8) (VOL - VOH)
tf
FIGURE 6. SLEW RATE DEFINITION
TOUT
V- < VTOUT < V+
300
400k
TXIN
GND < TXIN < VCC
V-
V+
VCC
FIGURE 7. TRANSMITTER
ICL232


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