HD26LS32

Rev.2.00, Jul.16.2004, page 10 of 14

This is because, since the termination resistance is normally matched to the transmission line characteristic impedance,

the value falls to several tens of hundreds of ohms, and the differential input pins are shorted by this termination

resistance. That is, the differential input voltage V

V

and the output becomes undetermined.

To prevent this, resistance R

of the termination resistance. Resistance R

and R

Inserting resistances R

but the following points must be noted.

• Smallest possible R

If this value is large, the receiver input sensitivity will fall.

• Largest possible R

If this value is small, the load on the driver will be large.

Figure 7 shows experimental differential input voltages for variations in R

"H"

Undetermined

Figure 5 Examples of Transmission Line Disconnection

Receiver

Driver

Figure 6 Method of Enhancing Fail-Safe Function

0.6

0.5

0.4

0.3

0.2

0.1

0

5

10

15

R1 (k

Ω)

100

kΩ

300

kΩ

Ta = 25°C

100

Ω

Figure 7 R