1A

1Y

2A

2Y

INPUT

OUTPUT

10

SN54HC14, SN74HC14

SCLS085I – DECEMBER 1982 – REVISED FEBRUARY 2016

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Copyright © 1982–2016, Texas Instruments Incorporated

10 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. Customers should

validate and test their design implementation to confirm system functionality.

10.1 Application Information

The SNx4HC14 device is a Schmitt-trigger input CMOS device that can be used for a multitude of inverting buffer

type functions. The application shown here takes advantage of the Schmitt-trigger inputs to produce a delay for a

logic output.

10.2 Typical Application

Figure 5. Simplified Application Schematic

10.2.1 Design Requirements

This device uses CMOS technology. Take care to avoid bus contention because it can drive currents that would

exceed maximum limits. Parallel output drive can create fast edges into light loads so consider routing and load

conditions to prevent ringing.

10.2.2 Detailed Design Procedure

This circuit is designed around an RC network that produces a slow input to the second inverter. The RC time

constant,

τ, is calculated from: τ = R×C

The delay time for this circuit will be between 1.2

τ and 0.42τ. It should be noted that the delay will be consistent

for each device, but since the switching threshold is only guaranteed between a minimum and maximum value,

the output pulse length will vary between devices. These values were calculated by using the minimum and

The resistor value should be chosen such that the maximum current from/to the SNx4HC14 is 4 mA.

•

Recommended input conditions:

–

Schmitt-trigger inputs allow for slow inputs.

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Recommended output conditions:

–

Load currents should not exceed 4 mA per output.