SN74HC595N 8-Bit Shift Register for LED and Digital Output Expansion

ElecSuppliers Part Number GuideAug 22, 2026

SN74HC595N is an 8-bit serial-in parallel-out shift register widely used to expand digital outputs in electronic systems. It allows a microcontroller to control multiple outputs using only a small number of communication lines.

Instead of connecting eight independent output signals directly to a microcontroller, the designer can send serial data to SN74HC595N and obtain eight parallel output signals from the register.

This makes the device particularly useful when an embedded system has limited GPIO resources but needs to control LEDs, displays, relays or other digital circuits.

What Is SN74HC595N?

SN74HC595N combines an 8-bit shift register with an output register.

Serial data is shifted into the device one bit at a time. After the required data has been transferred, the output register can update the parallel outputs.

This architecture separates data shifting from output updating.

As a result, the outputs can remain stable while new data is being loaded into the shift register.

This feature is useful for LED displays and other applications where changing individual outputs during data transmission could create unwanted visual or electrical effects.

SN74HC595N Pin Functions

SN74HC595N uses a standard DIP package configuration, making it convenient for prototypes, educational projects and through-hole circuit boards.

The important signals include serial data input, serial clock, latch control and output enable.

The serial data input receives the individual bits.

The clock signal determines when each bit is shifted into the internal register.

The latch control transfers the shifted data to the output register.

The output enable function controls whether the parallel outputs are active.

Understanding these signals is important when connecting SN74HC595N to an MCU.

SN74HC595N With Arduino and Microcontrollers

One of the most common applications for 74HC595 devices is expanding microcontroller outputs.

A microcontroller can communicate with SN74HC595N using only a few GPIO pins.

For example, three control signals can be used for data, clock and latch functions while eight output channels are provided by the shift register.

Multiple SN74HC595N devices can also be connected in a chain.

The output of one shift register can feed the serial input of another device, allowing the controller to manage a larger number of outputs without requiring additional MCU GPIO pins.

SN74HC595N LED Control

LED control is one of the most common uses for SN74HC595N.

Eight LEDs can be connected to the eight output channels, with each output representing an individual LED state.

The MCU sends an 8-bit pattern to the shift register.

For example, different binary patterns can create different indicator combinations.

When multiple SN74HC595N devices are connected in series, larger LED indicator panels can be controlled using the same basic serial interface.

For applications requiring significant LED current, external driver components should be considered rather than connecting high-current loads directly to the shift-register outputs.

SN74HC595N Seven-Segment Display

SN74HC595N can also be used with seven-segment displays.

A single display requires several control signals, and multiple digits can quickly consume MCU GPIO resources.

A shift register can reduce the number of direct connections required between the microcontroller and display circuitry.

The MCU sends the required segment pattern serially to SN74HC595N and updates the output register when the complete pattern has been transferred.

For multi-digit displays, additional multiplexing circuitry can be used together with one or more shift registers.

SN74HC595N Relay and Digital Control

The parallel outputs can also control external switching circuits.

For example, an SN74HC595N can provide control signals for relay-driver circuits, transistor stages or other digital interfaces.

The shift register itself should not be treated as a high-power switching device.

When controlling relays, motors or other loads, an appropriate external driver should be placed between the SN74HC595N output and the load.

This arrangement allows the shift register to handle digital logic while the external driver handles the required load current.

SN74HC595N Output Expansion

GPIO expansion is particularly useful in embedded products where the number of available MCU pins is limited.

A microcontroller may already use several pins for communication, sensors and other peripherals.

Adding an SN74HC595N can provide additional digital outputs without requiring a larger MCU.

The same serial interface can control several registers when additional outputs are needed.

This approach can reduce PCB complexity and allow designers to maintain a smaller microcontroller package.

SN74HC595N Cascading

One of the most useful characteristics of the 74HC595 architecture is cascading.

The serial output from one device can be connected to the serial input of the next.

The controller can then send a longer stream of bits through the chain.

For example, two shift registers provide 16 parallel output positions, while three provide 24.

The controller still uses the same basic clock and latch signals.

The main consideration is that a longer chain requires more serial data to be transmitted before the outputs are updated.

SN74HC595N SPI Interface

SN74HC595N does not require a dedicated SPI peripheral, but its serial data and clock architecture can be driven conveniently using an MCU's SPI interface.

The SPI output can provide the serial data and clock signals, while another GPIO controls the latch.

This can make firmware simpler because the MCU hardware handles the serial data transfer.

The exact connection depends on the MCU and the system's timing requirements.

SN74HC595N Output Enable

The output-enable function provides additional flexibility.

The parallel outputs can be disabled when required, allowing the system to temporarily disconnect the register outputs from the external circuit.

This can be useful during startup, data updates or multiplexed display applications.

It can also be useful when several devices share external control circuitry and their outputs need to be enabled or disabled at specific times.

SN74HC595N Operating Voltage

SN74HC595N belongs to the HC logic family and is designed for operation across a range of supply voltages.

When connecting it to a microcontroller, the logic-high and logic-low thresholds should be checked against the MCU's actual output levels.

This is especially important when mixing different logic-voltage domains.

For a reliable design, the shift register's input thresholds, supply voltage and MCU output characteristics should all be considered together.

SN74HC595N Timing

Timing becomes increasingly important when SN74HC595N is operated at higher clock speeds or when several devices are cascaded.

The serial data must be stable in relation to the clock signal.

After all required bits have been shifted into the register, the latch operation transfers the new state to the outputs.

In most simple MCU applications, the timing requirements are straightforward. However, high-speed designs should verify the relevant setup, hold and propagation characteristics.

SN74HC595N Package Selection

SN74HC595N is commonly associated with a through-hole DIP package.

This makes it convenient for prototyping and educational development because it can be inserted directly into a breadboard or socket.

For compact production PCBs, designers may prefer a surface-mount version from the same logic family.

When selecting a different package variant, the exact ordering code should be checked because package, pin arrangement and electrical characteristics can vary between related devices.

SN74HC595N Replacement

When searching for an SN74HC595N replacement, engineers should first determine whether they need an exact DIP package or simply an electrically compatible 74HC595 device.

Important parameters include supply voltage, input thresholds, output characteristics, clock speed, output enable behavior and package configuration.

A replacement should also maintain the same functional relationship between serial input, clock, latch and parallel outputs.

For an existing PCB, pin compatibility is particularly important.

SN74HC595N Applications

SN74HC595N can be used in many digital control applications, including:

LED indicator boards, seven-segment displays, digital control panels, GPIO expansion, relay-driver interfaces, hobby electronics, embedded controllers and simple automation equipment.

Its main advantage is not computational capability but efficient digital output expansion.

A small MCU can therefore control many external devices while keeping the number of dedicated GPIO connections relatively low.

SN74HC595N Design Considerations

SN74HC595N is a good choice when an application needs more digital outputs than the microcontroller can conveniently provide.

The designer should determine the number of outputs required, the required update speed and the current needed by each external load.

For LEDs and other loads that require more current than the logic outputs should provide, external transistor or driver stages should be used.

For multiple cascaded registers, the total serial transfer time should also be considered.

Choosing SN74HC595N

SN74HC595N remains a useful building block for digital output expansion because its interface is simple and its operation is easy to integrate with common microcontrollers.

It is particularly attractive for applications where several LEDs, indicators, display segments or control signals are required but adding a larger MCU would be unnecessary.

For a new design, engineers should select the package and logic-voltage version according to the PCB and MCU requirements. For an existing design, the original package, pinout and output requirements should be verified before choosing an alternative 74HC595 device.