4

Transmitter

The HS-245RH transmitters have two inputs per transmitter,

either of which is low while the other is open during normal

operation and both inputs are open during standby. For

optimum transmitter performance, the “off” input should be

open circuit rather than being pulled towards +5V, because

this will reduce the “on” output data current. On the other

hand, the “on” and “off” output data current will increase if

the “off” input is held below its open circuit voltage. Open

collector gates such as the 7401 and 7403 or 7405 Hex-

Inverter are suitable for driving the HS-245RH transmitter

inputs. By using 2-input gates as shown in Figure 4, an

enable line can be provided so that more than one

transmitter may be connected to a line for time sharing.

When the enable line is low the transmitter will be disabled

and will present a high impedance to the transmission line as

well as requiring very little power supply current.

Complementary input signals may be derived from high

speed inverter gates as shown, or by using the

complementary outputs of a flip-flop. When the transmitter is

connected near the midpoint of a long transmission line or to

a line with terminations at both ends, two transmitter

sections should be paralleled with respective inputs and

outputs connected together in order to drive the reduced

impedance. This parallel transmitter technique can also be

used to increase the data rate on long transmission lines.

TABLE A. GENERAL TRANSMITTER/RECEIVER CHARACTERISTICS

TRIPLE LINE TRANSMITTER

PARAMETER

HS-245RH

UNITS

COMMENTS

Operating Temperature Range

-55 to 125

“ON” Output Current

1.0 Min

mA

Over Full Temperature Range

Power Supply Current

7.0 Max

mA

Per Transmitter Section

Standby Current

33 Max

µA

Per Transmitter Section

Propagation Delay

14 Max

ns

Over Full Temperature Range

TRIPLE LINE RECEIVER

PARAMETER

RECEIVER TYPE

LIMITS

UNITS

COMMENTS

Operating Temperature Range

HS-246RH/248RH

-55 to 125

Power Supply

ICC (VCC = +5.0V)

HS-246RH/248RH

2.6

mA

Per Receiver Section

Propagation Delay

All Receivers

30

ns

Over Full Temperature Range

Input Impedance and

Output Circuit

HS-246RH

INPUT

Ω

OUTPUT

100

Open Collector

HS-248RH

Hi-Z

6K Pull-Up Resistor

-5V

OUT

+5

GND

1/3

HS-246RH

+5V

GND

2K-6K FOR TTL DRIVE

REQUIRED FOR HS-246RH

OUT

1/3

HS-248RH

-5V

+5V

GND

IN

ENABLE

G1

1/3

HS-245RH

G2

G3

FIGURE 4. TYPICAL DATA TRANSMISSION SYSTEM

HS-245RH, HS-246RH, HS-248RH