SN74HC595N 8-Bit Shift Register Pinout, Features, Circuit, and Datasheet

The SN74HC595N is an 8-bit serial-in, parallel-out shift register with an 8-bit storage register and 3-state output manufactured by Texas Instruments (TI). This IC is designed to expand digital I/O capabilities efficiently, making it ideal for driving LEDs, displays, and interfacing with microcontrollers. Housed in a PDIP-16 package, the SN74HC595N supports high-speed serial communication while minimizing the number of required microcontroller pins.

Overview of SN74HC595N

The SN74HC595N is an 8-bit shift register with serial-in and parallel-out functionality paired with an 8-bit D-type storage register. This storage register features parallel 3-state outputs for versatile applications. The design includes separate clock inputs for the shift register and the storage register, ensuring precise control. The shift register is equipped with a direct clear (SRCLR) input for quick resetting, a serial (SER) input for data entry, and cascading serial outputs for extending functionality. When the output-enable (OE) input is set high, the parallel outputs switch to a high-impedance state.

SN74HC595N Pinout

Pin Configuration and Functions

SN74HC595N CAD Model

SN74HC595N Features

• 8-Bit Serial-In, Parallel-Out Shift Register: Facilitates efficient data handling and output.
• Wide Operating Voltage Range: Functions seamlessly across 2 V to 6 V.
• High-Current 3-State Outputs: Capable of driving up to 15 LSTTL loads.
• Low Power Consumption: Maximum ICC of 80 µA ensures energy efficiency.
• Fast Propagation Delay: Typical tpd of 13 ns for rapid performance.
• Output Drive Capability: Provides a ±6-mA drive at 5 V for robust output.
• Minimal Input Current: Input current remains under 1 µA, reducing overall power usage.
• Direct Clear on Shift Register: Enables quick reset functionality.
• MIL-PRF-38535 Compliance: For compliant products, all parameters are rigorously tested. Other products may not undergo testing for all parameters during production.

SN74HC595N Specifications

SN74HC595N Functional Block Diagram

Absolute Maximum Ratings

Typical Application Schematic

How Does the SN74HC595N Shift Register Work?

The SN74HC595N features two 8-bit registers that function as "memory containers." These are the Shift Register and the Storage/Latch Register.

Shift Register Behavior

Each clock pulse initiates two key actions within the shift register:

1. Bit Shifting: The bits stored in the shift register shift left by one position. For instance, the value in bit 0 moves to bit 1, bit 1 moves to bit 2, and so forth.
2. Data Input: Bit 0 of the shift register receives the current state of the DATA pin. If the DATA pin is high during the rising edge of the clock pulse, a 1 is pushed into the register; otherwise, a 0 is inserted.

This process repeats continuously as long as clock pulses are supplied.

Latch Functionality

When the latch pin is activated, the contents of the shift register are transferred to the storage/latch register. Each bit in the storage register corresponds to one of the IC's output pins (QA through QH). As a result, any change in the storage register's value directly updates the output states of these pins.

Where to Use SN74HC595N?

The SN74HC595N is an 8-bit Serial-In, Parallel-Out Shift Register, designed to accept serial input data and control eight parallel output pins. It is particularly useful when the GPIO pins on a microcontroller or microprocessor are insufficient to handle the required number of outputs.

Common applications include:

• LED Control: Ideal for projects requiring control of multiple LEDs with limited GPIO resources.
• LCD Interface: This can act as the data bits for LCDs, simplifying connections.
• Driving 5V Loads: Suitable for controlling 5V loads, such as relays, through a 3.3V microcontroller, as its high-level voltage is only 3.15V.

This IC is an excellent choice for saving GPIO pins while maintaining versatile output control.

How to Use an SN74HC595N?

The SN74HC595N is often paired with microcontrollers or microprocessors to expand GPIO capabilities. It requires only three pins from the MCU: Clock, Data, and Latch. The IC operates across a wide voltage range of 2V to 6V.

Typical Application Circuit

In the circuit:

• Pin 11 (Clock): Sends constant timing pulses.
• Pin 14 (Data): Carries information about which output pins should be high or low.
• Pin 12 (Latch): Updates the outputs when set high. This pin can also remain permanently high for continuous updates.

The clock pulses synchronize the data, and the latch applies it to the output pins. For example, sending the binary value 0b10110011 sets the respective output states accordingly.

Master Reset (MR)

• Usage: Clears the outputs.
• Configuration: Held high to Vcc when not in use or brought low for resetting outputs.

One key advantage of the SN74HC595N is its ability to be cascaded to control more than eight outputs. To achieve this:

• Pin 9 (Q7'): Connects to the Data pin of a second SN74HC595N IC.
• The first 8 bits from the MCU control the outputs of the first IC, while the next 8 bits control the second IC.

This setup enables efficient expansion of output capabilities while maintaining simplicity in design.

SN74HC595N Applications

Network Switches

The SN74HC595N shift register is commonly used in network switches for expanding the control of multiple relays, LEDs, or other devices that need to be activated or monitored. It allows for the efficient control of a large number of ports or status indicators from a microcontroller (MCU) or microprocessor (MPU) with limited GPIO pins. By serially shifting data, the SN74HC595N helps minimize the pin count required for controlling complex switching functions in networking hardware, improving the scalability and flexibility of network switches.

Power Infrastructure

In power infrastructure systems, particularly for smart grids and control systems, the SN74HC595N is used to control and monitor multiple components with minimal pin usage. These may include voltage regulators, circuit breakers, and power distribution panels. By utilizing its shift-register capabilities, the SN74HC595N can cascade control signals across various subcomponents, ensuring reliable performance in large-scale power management applications. This capability helps streamline the design of control systems that need to scale while keeping power consumption and wiring minimal.

LED Displays

SN74HC595N is widely used in LED display applications, where it is employed to drive multiple LEDs or a matrix of LEDs. The shift register allows serial data to control large numbers of LEDs, reducing the need for excessive wiring and GPIO pins on the controlling MCU or MPU. Whether it's for alphanumeric displays, status indicators, or large-scale signage, the SN74HC595N helps to simplify the design while ensuring that each LED can be individually addressed, all while maintaining efficient power usage and control logic.

Servers

In server applications, the SN74HC595N shift register facilitates the control of diagnostic LEDs, fan speeds, and other status indicators on server racks. By using the serial-in and parallel-out configuration of the SN74HC595N, servers can manage multiple indicators and sensors with a limited number of control pins. This is particularly beneficial in server management systems, where space and pin count are often constrained. The shift register helps maintain efficient communication between the server's MCU/MPU and the various components that need to be monitored and controlled.

Expand the GPIO Pin on an MCU/MPU

The SN74HC595N is primarily used to expand the General Purpose Input/Output (GPIO) capabilities of microcontrollers (MCUs) or microprocessors (MPUs). When a system needs more output pins than the MCU/MPU can provide, the SN74HC595N allows the addition of several output pins without the need for additional microcontroller resources. This is achieved by serially shifting data through the chip, enabling the control of multiple devices such as LEDs, motors, or relays. It is particularly useful in applications where the microcontroller is limited in terms of available pins but needs to control a large number of outputs.

Cascading Applications

Cascading refers to linking multiple SN74HC595N shift registers together to expand the number of controlled outputs further. In applications requiring more outputs than a single shift register can provide, cascading multiple SN74HC595N units allows the user to control a virtually unlimited number of devices with just a few control lines. This feature is commonly used in large-scale projects, such as driving extensive LED matrices, controlling large numbers of motors or relays, or interfacing with various other hardware components in a modular fashion, all from a single MCU/MPU.

High Logic Level Controller

The SN74HC595N shift register can be used as a high logic level controller to interface low-voltage microcontrollers or microprocessors with high-voltage systems. This capability is important in applications where the control signals need to drive higher-voltage devices, such as motors, high-power LEDs, or other industrial equipment. The SN74HC595N's ability to handle higher output logic levels ensures that the signal integrity and power requirements of the system are met while using lower-voltage control signals, thus protecting the MCU/MPU from potentially damaging high voltages.

Advantages and Disadvantages

SN74HC595N Advantages

• Low Pin Count Requirement: Only 3 pins are needed for serial communication (SER, SRCLK, RCLK).
• Expandable Outputs: Cascading multiple ICs allows limitless output expansion.
• Stable Output State: Data is latched for stable parallel output.
• Wide Operating Voltage: Compatible with a variety of digital systems.
• Cost-Effective Solution: Reduces the need for multiple GPIO pins on microcontrollers.

SN74HC595N Disadvantages

• Limited Current Drive: Maximum current per output pin is limited.
• Fixed Configuration: Only supports 8-bit parallel output without reconfiguration.

SN74HC595N Equivalents/Alternatives

SN74HC595N Package

The PDIP-16 (Plastic Dual In-line Package) is a through-hole mounting package. It provides:

• Ease of Prototyping: Ideal for breadboards and prototyping boards.
• Mechanical Stability: Reliable solder connections for permanent circuits.
• Good Thermal Dissipation: Suitable for medium-power applications.

SN74HC595N Manufacturer

Texas Instruments (TI) is a global leader in semiconductor manufacturing, offering a wide range of analog and embedded processing solutions. The SN74HC595N is part of TI's extensive portfolio of digital logic ICs, known for their reliability and high performance.

SN74HC595N Datasheet

The datasheet includes detailed specifications, performance graphs, and guidelines for proper implementation. It provides design recommendations, including capacitor selection, thermal considerations, and PCB layout optimization for achieving optimal performance.

SN74HC595N vs. 74HCT595

Here’s a detailed comparison table for SN74HC595N vs. 74HCT595:

Key Differences:

1. Voltage Levels: SN74HC595N supports a wider supply voltage range (2V–6V), while 74HCT595 operates in a narrower range (4.5V–5.5V).
2. Logic Compatibility: SN74HC595N works well with CMOS logic levels, whereas 74HCT595 is optimized for TTL logic compatibility.
3. Switching Speed: 74HCT595 typically offers faster switching speeds and lower propagation delays.

Both ICs are commonly used for serial-to-parallel data conversion, such as driving LEDs, seven-segment displays, or expanding I/O ports in microcontroller applications.

SN74HC595N vs. 74HC164

Here’s a detailed comparison table for SN74HC595N vs. 74HC164:

Key Differences:

1. Latch Feature: The SN74HC595N includes an output latch, allowing the outputs to hold their state independently of further serial data shifting. The 74HC164 lacks this feature.
2. Serial Input: The SN74HC595N has a single serial input, while the 74HC164 uses two AND-ed inputs for serial data.
3. Output Control: The SN74HC595N supports tri-state outputs for better bus interfacing, whereas the 74HC164 has push-pull outputs only.
4. Pin Count: The SN74HC595N has 16 pins, while the 74HC164 has 14 pins, making it more compact.

Best Use Cases:

• SN74HC595N: Ideal for applications requiring output latching and tri-state outputs, such as controlling multiple devices like LED displays or I/O expansion.
• 74HC164: Better suited for applications where continuous serial-to-parallel conversion is required without the need for latched outputs.

Both ICs are widely used in digital electronics, but their differences make them suitable for specific application scenarios.

Conclusion

The SN74HC595N is a versatile 8-bit shift register with a storage register and 3-state output, making it an essential component for expanding digital I/O in embedded systems. Its compact PDIP-16 package, high-speed operation, and cascading capability make it ideal for driving displays, LEDs, and other digital interfaces in consumer, industrial, and automotive applications.