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, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

In this application, three 2-input OR gates are combined to produce a 4-input OR gate function as shown in

Typical application block diagram. The fourth gate can be used for another application in the system, or the

inputs can be grounded and the channel left unused.

The SN74HCS32 is used to directly control the Enable pin of a fan driver. The fan driver requires only one

input signal to be HIGH before being enabled, and should be disabled in the event that all signals go LOW. The

4-input OR gate function combines the four individual overheat signals into a single active-high enable signal.

Temperature sensors can often be spread throughout a system rather than being in a centralized location. This

would mean longer length traces or wires to pass signals through leading to slower edge transitions. This makes

the SN74HCS32 ideal for the application since it has Schmitt-trigger inputs that do not have input transition rate

requirements.

9.2 Typical Application

EN

Device 1

Overheat

Fan

Driver

Device 2

Overheat

Device 3

Overheat

Device 4

Overheat

Figure 9-1. Typical application block diagram

9.2.1 Design Requirements

9.2.1.1 Power Considerations

Ensure the desired supply voltage is within the range specified in the Recommended Operating Conditions. The

supply voltage sets the device's electrical characteristics as described in the Electrical Characteristics.

The positive voltage supply must be capable of sourcing current equal to the total current to be sourced by all

any transient current required for switching. The logic device can only source as much current as is provided by

Maximum Ratings.

The ground must be capable of sinking current equal to the total current to be sunk by all outputs of the

required for switching. The logic device can only sink as much current as can be sunk into its ground connection.

Be sure not to exceed the maximum total current through GND listed in the Absolute Maximum Ratings.

SN74HCS32

SCLS781C – JANUARY 2020 – REVISED DECEMBER 2021

www.ti.com

10

Submit Document Feedback

Copyright © 2021 Texas Instruments Incorporated

Product Folder Links: SN74HCS32