Vcc

Unused Input

Input

Output

Input

Unused Input

Output

10

SN74LS07

SDLS021D – MAY 1990 – REVISED APRIL 2016

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11 Layout

11.1 Layout Guidelines

When using multiple bit logic devices, inputs must never 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 3 of the 4 buffer gates are used. Such input pins must not be

left unconnected because the undefined voltages at the outside connections result in undefined operational

states. Figure 6 specifies 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 must be

applied to any particular unused input depends on the function of the device. Generally they are tied to GND or

VCC, whichever makes more sense or is more convenient. It is generally acceptable to float outputs, unless the

part is a transceiver.

11.2 Layout Example

Figure 6. Layout Diagram