Copyright © 2016, Texas Instruments Incorporated

14

SN5414, SN54LS14, SN7414, SN74LS14

SDLS049C – DECEMBER 1983 – REVISED NOVEMBER 2016

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Product Folder Links: SN5414 SN54LS14 SN7414 SN74LS14

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Copyright © 1983–2016, Texas Instruments Incorporated

9 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.

9.1 Application Information

The SNx414 and SNx4LS14 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 input.

9.2 Typical Application

Figure 28. Simplified Application Schematic

9.2.1 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.

9.2.2 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 = RC.

The delay time for this circuit is from tdelay(min) = –ln |1 – VT+(min) / VCC| τ to tdelay(max) = –ln |1 – VT+(max) / VCC| τ. It

must be noted that the delay is consistent for each device, but because the switching threshold is only ensured

between the minimum and maximum value, the output pulse length varies between devices. These values must

be calculated by using the minimum and maximum ensured VT+ values in the Electrical Characteristics.

The resistor value must be chosen such that the maximum current to and from the SNx414/SNx4LS14 is 8 mA at

5-V VCC.