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Nov 21 2020

Introduction to 74HC164: An 8 Bits Shift Register [FAQ]

74HC164 Description

The 74HC164 is an 8-bit serial-in/parallel-out shift register. The device features two serial data inputs (DSA and DSB), eight parallel data outputs (Q0 to Q7). Data is entered serially through DSA or DSB and either input can be used as an active HIGH enable for data entry through the other input. Data is shifted on the LOW-to-HIGH transitions of the clock (CP) input. A LOW on the master reset input (MR) clears the register and forces all outputs LOW, independently of other inputs. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.



74HC164 Description

74HC164 Pin Configuration and Functions

74HC164 Features

74HC164 Functional Block Diagram

74HC164 Applications

Differences Between 74HC164 and 74HC595

74HC164 Package Outline

Component Datasheet



74HC164 Pin Configuration and Functions

74HC164 Pinout

   74HC164 Pinout

Pin Functions:

74HC164 Pin Functions

74HC164 Features

  • Wide supply voltage range from 2.0 to 6.0 V
  • CMOS low power dissipation • High noise immunity
  • Input levels:  1. For 74HC164: CMOS level   2.  For 74HCT164: TTL level
  • Gated serial data inputs
  • Asynchronous master reset
  • Complies with JEDEC standards
  • JESD8C (2.7 V to 3.6 V)
  • JESD7A (2.0 V to 6.0 V)
  • Latch-up performance exceeds 100 mA per JESD 78 Class II Level B
  • ESD protection:  1. HBM JESD22-A114F exceeds 2000 V   2. MM JESD22-A115-A exceeds 200 V
  • Multiple package options
  • Specified from -40 °C to +85 °C and -40 °C to +125 °C.

74HC164 Functional Block Diagram

74HC164 functional block diagram

74HC164 Applications

  • Programable Logic Controllers
  • Appliances
  • Video Display Systems
  • Output Expander

Differences Between 74HC164 and 74HC595

  • 74HC595 Pinout

  • 74HC595 Pin Functions

Pin No.


Name and Function


QA to QH

Data output



Ground (0V)



Serial data output



Shift register clear input



Shift register clock input



Storage register clock input



Output enable input



Serial data input



Positive supply voltage


  • 74HC595 has a latch, so the output can remain unchanged during the shift; 74HC164 has no latch, so it changes every time a shift clock is generated. This is the biggest difference between the two
  • 74HC595 uses special Q7 pin to realize multi-chip cascade; 74HC164 directly uses output pin Q7 to cascade
  • 74HC595 has enable OE, when OE is invalid, the output pin is high impedance; while 74HC164 has no enable pin
  • The reset of 74HC595 is for the shift register. If you want to reset the LATCH register, you must load the shift register content into the latch register on the rising edge of ST_CP; that is to say: 74HC595 reset is synchronous, 74HC164 reset is asynchronous , So the reset of 74HC164 is easier
  • 74HC164 has a corresponding 74HC165 parallel-to-serial chip.

74HC164 Package Outline

  • Package outline SOT108-1 (SO14)

74HC164 Package


  • Package outline SOT337-1 (SSOP14)

74HC164 Package


  • Package outline SOT402-1 (TSSOP14)

74HC164 Pacakge


  • Package outline SOT762-1 (DHVQFN14)

74HC164 Package

Component Datasheet

74HC164 Datasheet


  • How does the 74HC164 transmit data in the microcontroller circuit?

  1. One pin of the single-chip microcomputer is like a faucet, and the data is sent one by one, that is, like the water from the faucet, dripping drop by drop. The 74H164 is like a small bowl receiving water. It is just full after receiving 8 drops of water. At this time, it is sent to the digital tube.
  2. The single-chip microcomputer must send an 8-bit (or more) data, if it is sent at the same time, it is a parallel transmission, if it is a bit by bit, it is a serial transmission. The data of the single-chip microcomputer is sent to the 74HC164 bit by bit, which is serial, and the 74HC164 sends the data to the digital tube at once, which is parallel. So 74HC164 plays a role from serial transmissionto paralleltransmission.
  • What is the difference between 74HC164D and 74HC164N MCU?

The D in 74HC164D represents a chip package. The N in 74HC164N means dual in-line plastic packaging.

  • What is the difference between 74HC164 and 74LS164, can they be used together?

74ls164 is a TTL circuit, the power supply voltage is 5V, the high-level output current Ioh is -0.4MA, and the low-level output current is 8MA.

74HC164 is a CMOS circuit, the power supply voltage is 2V ~ 6V, the output drive current can reach plus or minus 20MA. If the power supply voltage you use is 5V and the output drive current is suitable for 74ls164, they can be used together.

  • What devices can 74hc164 be replaced with?

74HC164 is a CMOS device with a power supply voltage of 2V-6V. It can be directly replaced by 74HCT164, 40H164. If the power supply voltage is 5V and the output drive current is small, it can also be replaced by 74164, 74LS164, 74F164, 74ALS164.

  • Which of 74LS164 and 74HC164 has higher driving capability?

74LS164 is a TTL device with a high-level driving capability of about 0.4mA and a low-level driving capability of about 8mA. 74HC164 is a CMOS device, with high-level and low-level drive capability up to 20mA. The above data comes from DATASHEET. But generally speaking, the high-level output capability of many CMOS devices is weak, smaller than TTL, and the low-level drive capability is stronger.

  • Can 74hc164n be used to drive the digital tube?

Of course, you can use the 164 chip to drive the nixie tube, which is mostly used in situations where the IO port resources are tight and the display data refresh of the nixie tube is slow. When designing the circuit, multiple 164 chips are used in cascade, no matter how many digital tubes are driven, only 2 IO ports of the single-chip microcomputer are occupied. It can be said that it is the most IO port-saving driving method, and it is still driven statically, without strobe and brightness Low phenomenon.

The disadvantage is that multiple 164s are used in cascade connection, which will cause the single-chip microcomputer to send a large amount of display data (1 byte per nixie tube) at one time when refreshing the display data. During this process, the nixie tube will be all on, although the data is sent The process duration is very short, but it still affects the display effect. It is recommended to turn off the digital tube when refreshing the data.

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