9.2.3 Application Curves

Time (ns)

0

15

30

45

60

75

90

100

-2

0

2

3.3

5

0

22

50

-1

1

4

Figure 9-2. Simulated Signal Integrity at the Reciever With Different Damping Resistor (Rd) Values

10 Power Supply Recommendations

The power supply can be any voltage between the minimum and maximum supply voltage rating located in

the Recommended Operating Conditions. Each VCC terminal should have a good bypass capacitor to prevent

power disturbance. A 0.1-μF capacitor is recommended for this device. It is acceptable to parallel multiple

bypass capacitors to reject different frequencies of noise. The 0.1-μF and 1-μF capacitors are commonly used in

parallel. The bypass capacitor should be installed as close to the power terminal as possible for best results, as

shown in the following layout example.

11 Layout

11.1 Layout Guidelines

When using multiple-input and multiple-channel logic devices inputs must not ever be left floating. In many

cases, functions or parts of functions of digital logic devices are unused; for example, when only two inputs of a

triple-input AND gate are used or only 3 of the 4 buffer gates are used. Such unused input pins must not be left

unconnected because the undefined voltages at the outside connections result in undefined operational states.

All unused inputs of digital logic devices must be connected to a logic high or logic low voltage, as defined by the

input voltage specifications, to prevent them from floating. The logic level that must be applied to any particular

unused input depends on the function of the device. Generally, the inputs are tied to GND or VCC, whichever

makes more sense for the logic function or is more convenient.

SN74HCS244

SCLS873B – JULY 2021 – REVISED OCTOBER 2022

www.ti.com

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