8 Detailed Description

8.1 Overview

This device contains six independent inverters with Schmitt-trigger inputs. Each gate performs the Boolean

function Y = A in positive logic.

8.2 Functional Block Diagram

xA

xY

8.3 Feature Description

8.3.1 Balanced CMOS Push-Pull Outputs

A balanced output allows the device to sink and source similar currents. The drive capability of this device

may create fast edges into light loads so routing and load conditions should be considered to prevent ringing.

Additionally, the outputs of this device are capable of driving larger currents than the device can sustain without

being damaged. It is important for the output power of the device to be limited to avoid damage due to

over-current. The electrical and thermal limits defined in the Section 6.1 must be followed at all times.

The CD74HC14 can drive a load with a total capacitance less than or equal to the maximum load listed in the

Section 6.6 connected to a high-impedance CMOS input while still meeting all of the datasheet specifications.

Larger capacitive loads can be applied, however it is not recommended to exceed the provided load value. If

larger capacitive loads are required, it is recommended to add a series resistor between the output and the

capacitor to limit output current to the values given in the Section 6.1.

8.3.2 CMOS Schmitt-Trigger Inputs

Standard CMOS inputs are high impedance and are typically modeled as a resistor from the input to ground

in parallel with the input capacitance given in the Section 6.5. The worst case resistance is calculated with the

maximum input voltage, given in the Section 6.1, and the maximum input leakage current, given in the Section

6.5, using ohm's law (R = V ÷ I).

The Schmitt-trigger input architecture provides hysteresis as defined by ΔVT in the Section 6.5, which makes

this device extremely tolerant to slow or noisy inputs. While the inputs can be driven much slower than standard

CMOS inputs, it is still recommended to properly terminate unused inputs. Driving the inputs slowly will also

increase dynamic current consumption of the device. For additional information regarding Schmitt-trigger inputs,

please see Understanding Schmitt Triggers.

CD74HC14, CD54HC14

SCHS129G – JANUARY 1998 – REVISED MAY 2021

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8

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