3-11

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

with respect to ground to produce a signal across C4 equal to

The output impedance of the voltage doubler section (V+) is

approximately 200

Ω, and the output impedance of the voltage

inverter section (V-) is approximately 450

Ω. A typical

application 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,

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

and the supply current is reduced to less than 10

µA. 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

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

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 specifications of

±5V minimum with the worst

case conditions of: all transmitters driving 3k

Ω minimum load

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 indefinitely. The

powered down output impedance is a minimum of 300

Ω with

Receivers

The receiver inputs accept up to

±30V while presenting the

required 3k

Ω to 7kΩ input impedance even if the power is off

1.3V which is within the

±3V limits, known as the transition

region, of the RS-232 specifications. The receiver output 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. 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.

+

-

C1

+

-

C3

+

-

C2

+

-

C4

S1

S2

S5

S6

S3

S4

S7

S8

GND

RC

OSCILLATOR

GND

GND

V- = -(V+)

C1-

VOLTAGE INVERTER

VOLTAGE DOUBLER

FIGURE 1. CHARGE PUMP

300

Ω

400k

Ω

V-

V+

FIGURE 2. TRANSMITTER

5k

Ω

GND

FIGURE 3. RECEIVER

HIN230 thru HIN241