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

In this application, the SN74HCS166 is used to increase the number of inputs on a microcontroller. Unlike other

I/O expanders, the SN74HCS166 does not need a communication interface for control. It can be easily operated

with simple GPIO pins.

Additionally, a second shift register may be used to read more than eight inputs by simply tying the output of one

register to the serial input of the other.

At power-up, the initial state of the shift registers is unknown. To give them a defined state, the shift register

needs to be cleared will need to be cleared by the microcontroller. This will initialize the shift register to all zeros.

9.2 Typical Application

Sensor

0

A

B

C

D

E

F

G

H

CLK INH

SER

CLK

MCU

GPIO0

GPIO1

GPIO2

Sensor

1

Sensor

2

Sensor

3

Sensor

4

Sensor

5

Sensor

6

Sensor

7

QH

SH/LD

CLR

GND

0.1 …F

VCC

GPIO3

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.

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SN74HCS166

SCLS843 – AUGUST 2020

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