Application Report
SCEA069A – May 2019 – Revised April 2020

Reduce Noise and Save Power with the New HCS LogicFamily
Dylan Hubbard
ABSTRACT
System designers are continuously striving to improve signal integrity, reduce power, and increase
robustness in Automotive, Industrial, Personal Electronics, and other electronic systems. The Texas
Instruments™ (TI) next-generation Schmitt-trigger Integrated High-speed CMOS family was designed toachieve these goals. This 2 to 6-V Logic family was developed to improve digital signal integrity insystems that are affected by noise inherent to the environment it is in. The integration of Schmitt-triggers
to all inputs eliminates a majority of the issues seen with logic devices that stem from normal CMOS
inputs. HCS accomplishes all this while maintaining a low power consumption.

1234Contents
Introduction ...................................................................................................................
Input/Output Characteristics ...............................................................................................
Power Consumption ........................................................................................................
Common Logic Applications with Less Power and More Noise Rejection ..........................................

2244

List of Figures
1Benefits of Schmitt-trigger Inputs in the HCS Logic Family ............................................................ 22Output driver resistance in High state .................................................................................... 3

3Output driver resistance in LOW state .................................................................................... 34

Typical output high voltage versus source current across common supply values ................................. 35Typical output low voltage versus sink current across common supply values ..................................... 36

Typical supply current versus input voltage across common supply values (2 V to 3.3 V) ........................ 47

Typical supply current versus input voltage across common supply values (4.5 V to 6 V) ........................ 48Motor controller reset logic control using SN74HCS08-Q1 ............................................................ 49Multiple push-button debounce using SN74HCS04 ..................................................................... 5

10Toggle Switch w/o Integrated Schmitt-triggers ........................................................................... 6

11Toggle Switch w/ Integrated Schmitt-triggers ............................................................................ 6
List of Tables

Trademarks
All trademarks are the property of their respective owners.

SCEA069A – May 2019 – Revised April 2020
Submit Documentation Feedback

Reduce Noise and Save Power with the New HCS Logic FamilyCopyright © 2019–2020, Texas Instruments Incorporated

1

Introduction

1

www.ti.com

Introduction
The High-speed CMOS, or HC, family of Logic devices has been the benchmark for 5-V CMOS systemdesign for nearly 4 decades. It is still being used in millions of different products today and will continue tobe for decades to come. It was designed with a solid architecture allowing it to be higher-speed and lowerpower compared to the technology that came before. It also utilizes a balanced output with lower drive toavoid any issues with undershoot or overshoot. Because of this, the HC family was used as a foundation
for TI's new, next-generation logic family designed with new process technology. The end result is theSchmitt-trigger Integrated High-Speed CMOS, or HCS, family.
The wide operating supply voltage range coupled with each device having a commercial and automotiveversion, makes the HCS family a very versatile solution for discrete logic. Not all new designs are createdfrom the ground up, but instead are built off previous design revisions. The pin-to-pin compatibility
between HC and HCS will make it easier for the designer to replace an HC device used on a previous
revision without having to redesign the layout.

2

Input/Output Characteristics

2.1

Schmitt-Trigger Inputs
TI developed the HCS family to improve performance and robustness over older technology. The best way
to do this is to eliminate very common issues encountered with normal CMOS inputs such as oscillations
from slow or noisy inputs and excessive power consumption due to slow inputs, refer to Implications ofSlow or Floating CMOS Inputs. With the integration of Schmitt-triggers on all inputs, these issues areavoided.
Schmitt-triggers provide benefits to power consumption and noise rejection on digital signals while notlimiting the speed at which the input signal transitions.

Voltage

OutputCurrent

Voltage

OutputCurrent

TimeVoltage

OutputVoltage

Input Voltage

Current

Response
Waveforms

TimeTime

Input Voltage

OutputSchmitt-trigger
CMOS Input

TimeTimeCurrent

Response
Waveforms

Supply Current

Standard
CMOS Input

Supply Current

Input Voltage

Supports Slow InputsInput
Voltage

Noise Rejection
Input
Voltage

Input Voltage
Waveforms

Input
Voltage

Low PowerTimeFigure 1. Benefits of Schmitt-trigger Inputs in the HCS Logic Family
Figure 1 illustrates the three benefits Schmitt-triggers provide with example input signals and the resulting
output waveforms. To learn more about the operation of Schmitt-triggers, please refer to theUnderstanding Schmitt Triggers application report and the Eliminate Slow or Noisy Input Signals Logic
Minute Video.

2Reduce Noise and Save Power with the New HCS Logic Family
Copyright © 2019–2020, Texas Instruments Incorporated

SCEA069A – May 2019 – Revised April 2020
Submit Documentation Feedback

Input/Output Characteristics

www.ti.com

2.2

Balanced Outputs
The HCS family provides balanced outputs capable of driving up to ±7.8 mA while maintaining a valid logic
level. Figure 2, Figure 3, Figure 4, and Figure 5 illustrate the typical output characteristics of the HCSfamily.
7046

Output Resistance (:)

65
60
55
50
45
40

VCC = 2 V
VCC = 3.3 V
VCC = 4.5 V
VCC = 6 V

4442

Output Resistance (:)

VCC = 2 VVCC = 3.3 V
VCC = 4.5 V
VCC = 6 V

40383634323035283026
2.55

7.5 10 12.5 15 17.5
Output Source Current (mA)

20

22.5

250

2.55

7.5 10 12.5 15 17.5
Output Sink Current (mA)

20

22.5

25

Figure 2. Output driver resistance in High state

Figure 3. Output driver resistance in LOW state

6

1.2

5

1

VCL Output Low Voltage (V)VOH Output High Voltage (V)04322V
2.5 V
3.3 V

1

4.5 V
5V
6V

0.8
0.6
0.4
2V
2.5 V
3.3 V

0.24.5 V
5V
6V000510152025
IOH Output High Current (mA)

3035Figure 4. Typical output high voltage versus source
current across common supply values

SCEA069A – May 2019 – Revised April 2020
Submit Documentation Feedback

05D00210152025
IOL Ouput Low Current (mA)

3035D001

Figure 5. Typical output low voltage versus sink current
across common supply values

Reduce Noise and Save Power with the New HCS Logic Family
Copyright © 2019–2020, Texas Instruments Incorporated

3

Power Consumption

3www.ti.com

Power ConsumptionThe HCS family utilizes new process technology to achieve a low power consumption. It has a maximum
ICC of 2 µA , making it the lowest compared to other popular 5-V logic families. The dynamic power
consumption also stacks up well to the other popular 5-V families with a Cpd of only 10 pF. For more
information on CMOS power consumption and how to calculate total power consumption, please refer tothe CMOS Power Consumption and Cpd Calculation application report.
0.2

ICC - Supply Current (mA)

0.16
0.14
0.12
0.1
0.08
0.06

ICC - Supply Current (mA)

VCC = 2 V
VI = 2 o 0 V
VCC = 2 V
VI = 0 o 2 V
VCC = 2.5 V
VI = 2.5 o 0 V
VCC = 2.5 V
VI = 0 o 2.5 V
VCC = 3.3 V
VI = 3.3 o 0 V
VCC = 3.3 V
VI = 0 o 3.3 V

0.18

0.04
0.02
00

0.4

0.8

1.2

1.6
22.4 2.8
VI - Input Voltage (V)

3.2

3.6

4

0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0

VCC = 4.5 V
VI = 4.5 o 0 V
VCC = 4.5 V
VI = 0 o 4.5 V
VCC = 5 V
VI = 5 o 0 V
VCC = 5 V
VI = 0 o 5 V
VCC = 6 V
VI = 6 o 0 V
VCC = 6 V
VI = 0 o 6 V

00.8

1.6D001

Figure 6. Typical supply current versus input voltage
across common supply values (2 V to 3.3 V)

2.4

3.2
4
4.8 5.6
VI - Input Voltage (V)

6.4

7.2

8D001

Figure 7. Typical supply current versus input voltage
across common supply values (4.5 V to 6 V)

4Common Logic Applications with Less Power and More Noise Rejection

4.1

ANDing Reset Signals for Motor Control
Schmitt-trigger inputs broaden the possible applications the logic devices in the HCS family. For example,
in Automotive powertrain or Industrial PLC applications, it is expected for the digital signals to be exposed
to a noisy environment. Large transient voltage spikes and other devices with harsh switching components
can cause an abundance of noise to show up on the digital signals in the system. This can be detrimental
to a system if erroneous data shows up for a logic reset control. The use case in Figure 8 illustrates how
the SN74HCS08-Q1 device becomes the perfect solution for a motor control reset in an Automotive Bodysystem.
Power Supply

Over CurrentDetection

Motor Controller
OCPG
ON/OFFRESETOTOn/Off Switch

OverTemp
Detection

Figure 8. Motor controller reset logic control using SN74HCS08-Q1

4Reduce Noise and Save Power with the New HCS Logic Family
Copyright © 2019–2020, Texas Instruments Incorporated

SCEA069A – May 2019 – Revised April 2020
Submit Documentation Feedback

Common Logic Applications with Less Power and More Noise Rejection

www.ti.com

The SN74HCS08-Q1 will be able to reject the noise coupled to the input signal up to the minimum
hysteresis spec, or ΔVT. If the noise is expected to be greater than the minimum hysteresis spec, thenadditional filtering can be applied to any input of this AND gate with no issue from the inherently slow
transition rate of the filtered signal. This also applies to signals that have to travel far distance over wire ortraces as these signals will be affected by parasitic capacitances causing them to have a slower transition
rate. If this logic control is being supplied with standby power, then the low power consumption of the HCS
family will save on the power budget given for devices loading the car battery.

4.2

Button Debounce for Multiple Push-buttons
Personal electronic systems can also capitalize on the low power consumption of the HCS family. If awireless speaker powered from a lithium battery has multiple push button controls, then the SN74HCS04
use case illustrated in Figure 9 is a perfect solution to easily debounce the button without additional
software effort.

SystemController

Figure 9. Multiple push-button debounce using SN74HCS04
Power efficiency is critical for these systems as to not rapidly drain the battery. The Schmitt-trigger powersavings and the great dynamic power performance incorporated into the HCS family, will allow for users toplay and pause music or turn the volume up without wasting battery life.

SCEA069A – May 2019 – Revised April 2020
Submit Documentation Feedback

Reduce Noise and Save Power with the New HCS Logic Family
Copyright © 2019–2020, Texas Instruments Incorporated

5

Common Logic Applications with Less Power and More Noise Rejection

4.3

www.ti.com

Momentary to Toggle Switch with Power-on ResetHCS logic devices not only provide more noise immunity and lower power operation to a variety ofapplications, but they can also turn common applications into more size efficient and lower cost solutions.
An example application would be turning a momentary switch into a toggle switch using a D-type flip-flop.
Toggle switches are typically large, mechanically complex and relatively expensive. It is desirable to use amomentary switch instead because they are small, mechanically simple and low cost. Some systems
require a toggle switch's functionality but are space or cost constrained and must use a momentary switch
instead. The SN74HCS74-Q1 has integrated Schmitt-trigger inputs that eliminate the need for a second ICfor signal conditioning, reducing the required board space and eliminating the added cost. This makes theSN74HCS74-Q1 an ideal device for converting a momentary switch into a toggle switch compared to a Dtype flip-flop in another family. Figure 10 shows the application diagram of a D-type flip-flop being usedwithout integrated Schmitt-triggers versus Figure 11 which shows the same application using theSN74HCS74-Q1.

VCC

VCC
R1R2R1VCC

C1VCC

C1C2VCC

VCC*R3R2*PRE

DCLKQ

Q
CLR
GND

C2VCC

C2VCC
PREDR3CLKQ

C3CLRQ
GND

OutputOutput* External IC(e.g. SN74LVC2G17-Q1)

Figure 10. Toggle Switch w/o Integrated Schmitt-triggers

6Figure 11. Toggle Switch w/ Integrated Schmitt-triggers

Reduce Noise and Save Power with the New HCS Logic Family
Copyright © 2019–2020, Texas Instruments Incorporated

SCEA069A – May 2019 – Revised April 2020
Submit Documentation Feedback

IMPORTANT NOTICE AND DISCLAIMERTI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCEDESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANYIMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRDPARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicablestandards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants youpermission to use these resources only for development of an application that uses the TI products described in the resource. Other
reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third
party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims,
damages, costs, losses, and liabilities arising out of your use of these resources.
TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either onti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicablewarranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2020, Texas Instruments Incorporated