hin237cp Intersil Corporation, hin237cp Datasheet - Page 11

• Manufacturer Part Number: hin237cp
• Description: +5v Powered Rs-232 Transmitters/receivers
• Manufacturer: Intersil Corporation

Detailed Description
The HIN230 thru HIN241 family of RS-232
transmitters/receivers are powered by a single +5V power
supply (except HIN231 and HIN239), feature low power
consumption, and meet all ElA RS-232C and V.28
specifications. The circuit is divided into three sections: The
charge pump, transmitter, and receiver.
Charge Pump
An equivalent circuit of the charge pump is illustrated in Figure
1. The charge pump contains two sections: the voltage
doubler and the voltage inverter. Each section is driven by a
two phase, 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 V
two, the voltage on C1 is added to V
across C3 equal to twice V
charged to 2V
with respect to ground to produce a signal across C4 equal to
-2V
The output impedance of the voltage doubler section (V+) is
approximately 200 , and the output impedance of the voltage
inverter section (V-) is approximately 450 . A typical
application uses 1 F 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,
increasing the values of the reservoir capacitors, C3 and C4,
lowers the ripple on the V+ and V- supplies.
During shutdown mode (HIN230, 235, 236, 240 and 241),
SHUTDOWN control line set to logic “1”, the charge pump is
turned off, V+ is pulled down to V
and the supply current is reduced to less than 10 A. The
transmitter outputs are disabled and the receiver outputs are
placed in the high impedance state.
Transmitters
The transmitters are TTL/CMOS compatible inverters which
translate the inputs to RS-232 outputs. The input logic
threshold is about 26% of V
at the input results in a voltage of between -5V and V- at the
output, and a logic 0 results in a voltage between +5V and (V+ -
0.6V). Each transmitter input has an internal 400k pullup
CC
. The charge pump accepts input voltages up to 5.5V.
OSCILLATOR
GND
V
CC
RC
CC
, and then during phase two, it is inverted
S1
S3
VOLTAGE DOUBLER
CC
CC
3-11
. During phase one, C2 is also
, or 1.3V for V
C1
C1-
CC
+
+
-
C1
CC
, V- is pulled up to GND,
, producing a signal
S2
S4
CC
CC
. During phase
= 5V. A logic 1
HIN230 thru HIN241
+
FIGURE 1. CHARGE PUMP
-
C3
V
CC
V+ = 2V
GND
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 specifications of 5V minimum with the worst
case conditions of: all transmitters driving 3k minimum load
impedance, V
temperature. The transmitters have an internally limited output
slew rate which is less than 30V/ s. The outputs are short
circuit protected and can be shorted to ground indefinitely. The
powered down output impedance is a minimum of 300 with
Receivers
The receiver inputs accept up to 30V while presenting the
required 3k to 7k input impedance even if the power is off
(V
1.3V which is within the 3V limits, known as the transition
region, of the RS-232 specifications. The receiver output is
0V to V
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. The receiver Enable
line EN, when set to logic “1”, (HIN235, 236, 239, 240, and
241) disables the receiver outputs, placing them in the high
impedance mode. The receiver outputs are also placed in
the high impedance state when in shutdown mode.
CC
2V applied to the outputs and V
CC
S5
= 0V). The receivers have a typical input threshold of
S7
GND < T
CC
-30V < R
VOLTAGE INVERTER
. The output will be low whenever the input is
T
V
CC
XIN
XIN
CC
V+
XIN
V-
R
GND
C2
C2
V
= 4.5V, and maximum allowable operating
< V
XIN
FIGURE 2. TRANSMITTER
CC
< +30V
+
+
-
-
CC
FIGURE 3. RECEIVER
C2
400k
S6
S8
5k
CC
= 0V.
GND < V
300
+
-
C4
V- < V
R
ROUT
OUT
T
TOUT
OUT
GND
V- = -(V+)
< V
< V+
CC