7 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

7.1 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 0.1μF capacitor is recommended for this device. Parallel multiple bypass capacitors to

reject different frequencies of noise is acceptable. 0.1μF and 1μF 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

Figure 7-1.

7.2 Layout

7.2.1 Layout Guidelines

When using multiple bit logic devices inputs should not ever float.

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 three of the four buffer gates are used. Such input pins

should not be left unconnected because the undefined voltages at the outside connections result in undefined

operational states. Specified below are the rules that must be observed under all circumstances. All unused

inputs of digital logic devices must be connected to a high or low bias to prevent them from floating. The logic

level that should be applied to any particular unused input depends on the function of the device. Generally they

will be tied to GND or VCC whichever make more sense or is more convenient. Floating outputs is generally

acceptable, unless the part is a transceiver. If the transceiver has an output enable pin it will disable the outputs

section of the part when asserted. This will not disable the input section of the I.O’s so they also cannot float

when disabled.

7.2.2 Layout Example

1

2

3

4

5

6

7

14

13

12

11

10

9

8

1CLR

1D

1PRE

1Q

1Q

GND

VCC

2CLR

2D

2PRE

2Q

2Q

GND

VCC

2CLK

1CLK

0.1

F

Unused input

tied to GND

Bypass capacitor

placed close to the

device

Avoid 90°

corners for

signal lines

Recommend GND flood fill for

improved signal isolation, noise

reduction, and thermal dissipation

Unused output

left floating

Unused inputs

tied to VCC

Figure 7-1. Example Layout for the in the SNx4ACT74 Package

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SN54ACT74, SN74ACT74

SCAS520J – AUGUST 1995 – REVISED APRIL 2025

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