INH

C B A

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

C

B

A

COM

CD4051B

Microcontroller

Input

Channel Select

Pull-down resistors (10

NŸ)

3.3 V

3.3 V

CD4051B, CD4052B, CD4053B

www.ti.com

SCHS047H – AUGUST 1998 – REVISED APRIL 2015

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 CD405xB multiplexers and demuliplexers can be used for a wide variety of applications.

9.2 Typical Application

One application of the CD4051B is to use it in conjunction with a microcontroller to poll a keypad. Figure 28

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, allowing for multiple simultaneous key-presses with very little power consumption. It also utilizes

very few pins on the microcontroller. The down side of polling is that the microcontroller must continually scan

the keys for a press and can do little else during this process.

Figure 28. The CD4051B 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 should be considered to prevent ringing.

Copyright © 1998–2015, Texas Instruments Incorporated

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Product Folder Links: CD4051B CD4052B CD4053B