SN74HC165N: 8-Bit Parallel-Load Shift Register

ElecSuppliers Part Number ComparisonAug 21, 2026

The SN74HC165N is an 8-bit parallel-load shift register designed to convert multiple parallel digital inputs into a serial data stream. It allows a microcontroller to monitor several digital signals while using only a small number of MCU pins.

The device is part of the 74HC logic family and combines eight parallel data inputs with serial data output, making it useful for digital input expansion, switch monitoring, control panels and embedded systems.

What Is the SN74HC165N?

The SN74HC165N is an 8-bit parallel-in, serial-out shift register.

Eight individual input pins allow digital states to be loaded into the internal register. Once the data has been loaded, the controller can shift the stored information out serially.

This architecture is useful when a microcontroller needs to read many digital signals but does not have enough available GPIO pins.

Instead of dedicating one MCU input to every switch or digital signal, multiple inputs can be collected by the SN74HC165N and transferred through a serial connection.

SN74HC165N 8-Bit Parallel Inputs

The device provides eight individual parallel data inputs designated A through H.

These inputs allow the logic state of multiple external signals to be captured into the shift register.

For example, eight push buttons, switches or digital status signals can be connected to the eight input channels. The microcontroller can then load the states into the register and read them sequentially.

This approach can significantly reduce the number of GPIO connections required on the main controller.

SN74HC165N Serial Data Output

After the parallel data has been loaded, the SN74HC165N shifts the stored information toward its serial output.

The MCU can read the individual bits sequentially using the clock signal.

This makes the device particularly convenient for systems that need to monitor multiple digital inputs but do not require all input states to be read simultaneously by dedicated MCU pins.

The serial output can also be connected to another shift register, allowing multiple devices to be arranged in a chain.

SN74HC165N Shift and Load Operation

The SN74HC165N provides a shift/load control function that determines whether the parallel inputs are being loaded or whether the stored information is being shifted.

When the load function is activated, the states of the eight parallel inputs are captured.

After loading is completed, the device can be placed into shift mode. Clock pulses then move the stored bits toward the serial output.

This separation between loading and shifting gives the host controller control over when a complete set of input states is captured.

SN74HC165N Clock Control

The SN74HC165N includes clock and clock-inhibit functions.

The clock determines when the stored data moves through the shift register, while the clock-inhibit input can be used to control whether shifting occurs.

This provides additional control when the device is integrated into a larger digital system.

The clock and control signals should be configured according to the required loading and shifting sequence so that the MCU receives the correct bit order.

SN74HC165N Operating Voltage

The SN74HC165N supports a supply-voltage range of 2V to 6V.

This makes it suitable for a variety of digital systems using common low-voltage logic supplies.

When connecting the device to a microcontroller, the logic-level compatibility between the MCU and the SN74HC165N should still be checked for the selected supply voltage.

The power supply should also be properly decoupled to reduce unwanted switching noise.

SN74HC165N Low Power Operation

The SN74HC165N is designed for low power consumption within the 74HC logic family.

TI specifies a maximum supply current of 80 µA for the device under its specified conditions.

Low static power consumption can be useful in embedded systems that need additional digital inputs without adding a significant continuous power load.

The total system power consumption will also depend on switching activity, external loads and the other components connected to the shift register.

SN74HC165N Cascading

Multiple SN74HC165N devices can be connected in series to expand the number of available digital inputs.

For example, two devices can provide sixteen parallel inputs while using a serial data path to the MCU. Additional registers can be added when more inputs are required.

This scalable architecture is useful for systems such as industrial control panels, keyboard interfaces and equipment with many digital status signals.

The firmware simply needs to clock the required number of bits through the connected registers.

SN74HC165N Applications

The SN74HC165N can be used in applications where multiple digital inputs need to be monitored with limited MCU GPIO resources.

Common applications include switch panels, button matrices, keypad interfaces, industrial control equipment, status monitoring and embedded control systems.

It can also be used to monitor multiple digital outputs from external circuits when the controller does not have enough direct input pins.

For systems with a large number of digital inputs, cascading several SN74HC165N devices can provide a simple and scalable input-expansion solution.

SN74HC165N Package

The SN74HC165N uses a 16-pin PDIP package.

The through-hole package can be convenient for prototypes, development boards, educational equipment and designs where through-hole assembly is preferred.

The complete SN74HC165N ordering code should be retained when specifying the component because other SN74HC165 variants use different package configurations.

For a PCB replacement, the package type and pin configuration should always be checked before selecting another variant.

SN74HC165N PCB Design Considerations

The SN74HC165N should have appropriate power-supply decoupling close to its supply pins.

Clock and serial-data traces should be routed carefully when the device is operated at higher switching speeds or when multiple shift registers are connected together.

External switches and mechanical inputs may also require appropriate pull-up or pull-down arrangements and debouncing.

For noisy industrial environments, the input conditioning circuit should be designed according to the electrical characteristics of the connected signals.

Choosing the SN74HC165N

The SN74HC165N is a practical choice when an embedded system needs additional digital inputs without consuming a large number of MCU GPIO pins.

Its eight parallel inputs, serial output, shift/load control, clock-inhibit function and wide 2V to 6V supply range make it useful for digital input expansion.

The device is especially suitable when several digital signals need to be read sequentially rather than through individual MCU inputs.

For procurement and BOM management, use the complete SN74HC165N Part Number when specifying the component so that the required PDIP package is clearly identified.