CD54HC4051F3A datasheet(23/49 Pages) TI

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S2S1S0

0 0 0

0 0 1

0 1 0

0 1 1

1 0 0

1 0 1

1 1 0

1 1 1

Ch 0

Ch 1

Ch 2

Ch 3

Ch 4

Ch 5

Ch 6

Ch 7

COM

CD74HC4051

Microcontroller

Polling Input

Channel Select

3.3V

VEE

GND

VCC

Pull-down resistors (10

NŸ)

CD54HC4051, CD74HC4051

CD54HCT4051, CD74HCT4051, CD54HC4052, CD74HC4052, CD54HCT4052

CD74HCT4052, CD54HC4053, CD74HC4053, CD54HCT4053, CD74HCT4053

www.ti.com

SCHS122M – NOVEMBER 1997 – REVISED MAY 2019

Product Folder Links: CD54HC4051 CD74HC4051 CD54HCT4051 CD74HCT4051 CD54HC4052 CD74HC4052

CD54HCT4052 CD74HCT4052 CD54HC4053 CD74HC4053 CD54HCT4053 CD74HCT4053

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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 CDx4HCx405x line of multiplexers and demultiplexers can be used for a wide variety of applications.

9.2 Typical Application

One application of the CD74HC4051 device is used in conjunction with a microcontroller to poll a keypad.

Figure 20 shows the basic schematic for such a polling system. The microcontroller uses the channel-select pins

to cycle through the different channels while reading the input to see if a user is pressing any of the keys. This is

a very robust setup that allows for simultaneous key presses with very little power consumption. It also uses very

few pins on the microcontroller. The down side of polling is that the microcontroller must frequently scan the keys

for a press.

Figure 20. CD74HC4051 Being Used to Help Read Button Presses on a Keypad

9.2.1 Design Requirements

These devices use CMOS technology and have balanced output drive. Take care to avoid bus contention

because it can drive currents that would exceed maximum limits. The high drive will also create fast edges into

light loads, so routing and load conditions must be considered to prevent ringing.

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