74HC164 8-Bit Parallel-Out Shift Register

7 April 2021 - 0 Comments

74HC164 8-Bit Parallel-Out Shift Register

74HC164 Pinout

74HC164 is a CMOS Level 8-Bit, two Serial inputs based and Parallel output Shift register that can be used to increase the output pins of the microcontroller unit. The specification can be found on the part number itself where 74 is derived from the 7400 logic family and the HC stands for the High-Speed CMOS operation.

Since it is 8-bit, it has 8 output pins which can be assumed as 8 output pins of any microcontroller unit. Thus, it can asynchronously have data serially in its input pins microcontrollers and provide output on 8 different output pins which can be further connected to Transistor switches, LEDs, or in other input pins of sensor or parallel interfaces.

One of the best use cases is controlling LED arrays or LCDs that support 8-bit parallel inputs. So, if in your application, you are running out of output pins, then this 74HC164 8-Bit Parallel out / serial-in shift register might be the right choice for you.

Other than this, it has a clear input as well.

This 14 pin Shift register has input voltage from 2V to 6V, which opens up a low voltage microcontroller application also. Thus, it can be used for 3.3V and 5V logic levels as well.

Pin Description of 74HC164

Pin no.	Pin name	The main function
1	A	Gated Serial Input 1
2	B	Gated Serial Input 2
3,4,5,6,10,11,12,13	Parallel Output (A-H)	Parallel Output Pins
9		Clear 1 Active-Low
7	GND	Ground Pin
8	CLK	Clock
14	VCC	Power Input PIn

Features and specification of 74HC164

8-bit, Parallel Out - Serial Input Shift register
Operating Voltage: 2V to 6V
Current Consumption: 100uA (max)
Output current Source: ±25mA
Input and Output Voltage is equal to Operating voltage (Can be 0 and VCC)
Minimum high-level Output Voltage: 4.4V @(Vcc=4.5V)
Maximum low-level Output Voltage: 0.1V @(Vcc=4.5V)
Maximum Clock Frequency: 54Mhz @4.5V
Available in 14-pin PDIP, FK, SSOP, CDIP, SOIC packages

Note: Complete technical details can be found in the 74HC164 Datasheet linked at the bottom of this page.

Alternative Product of 74HC164

Alternative products for the 74HC164 shift register are listed below:

74HC595
74HCS594
74HCS596

How to use 74HC164

74HC164 is easy to interface with. It is very useful for microcontrollers or microprocessors. This device takes Two inputs across an AND Gate and sends the data to its 8-bit parallel output pins. To provide the serial data into its parallel output pins, it requires a clock signal. The 8-bit data output is only available when Pin 1, B is enabled. To provide the clocking, a low-to-high transition can be applied in CLK input while sending the data over its serial input pins. Each new cycle of data is started with the high to low transition in the Clear Pin pin.

The state of the pins can be seen properly in the image given below, which is taken from the 74HC164 datasheet.

74HC164 State Graph

The CLK pin is constantly getting the Clock input, the data enable pin B is high and the data input pin A is receiving the serial data which is reflected on the 8-bit parallel port.

For connection, the schematic given below can be useful for interfacing with a microcontroller or microprocessor.

74HC164 Interfacing Circuit Diagram

As we can see in the above image, only 4 pins are required for connecting the 74HC164 with a microcontroller or microprocessor. Appropriate logic levels enable the data input from 8 buttons, and the serial data can be harvested from the output pin of the 74HC164.