💡74HC595:SHIFT REGISTER

🤔IN SHORT

⚡The 74HC595 is a popular integrated circuit (IC) that serves as a shift register with output latches. It is commonly used in electronic projects for expanding the number of available output pins of a microcontroller or driving multiple LEDs or other digital components.

  • ✨Serial to Parallel Conversion: The 74HC595 is designed for serial-to-parallel data conversion. Data is shifted into the shift register serially through a single input line, typically synchronized with a clock signal.
  • ✨Output Latches: The IC has an internal storage register known as output latches that hold the data after it has been shifted into the shift register. The data from the latches can be transferred to the output pins by a latch enable signal.
  • ✨Cascade Capability: Multiple 74HC595 ICs can be daisy-chained together, allowing for further expansion of the number of output pins. This cascading feature enables control of a large number of outputs using just a few pins of a microcontroller.
  • ✨High-Speed Operation: The 74HC595 operates at high speeds and can handle data rates of up to 100 MHz, making it suitable for applications with fast data transfers.
  • ✨Wide Operating Voltage Range: It operates with a wide voltage range, typically between 2V and 6V, making it compatible with a variety of microcontrollers and logic levels.
  • ✨Output Drive Capability: The 74HC595 can drive outputs directly, providing a maximum output current of around 35mA per output pin, which is useful for driving LEDs or other digital components.
  • ✨Simple Control Interface: The IC requires only a few control signals, including clock, data, and latch enable, making it relatively easy to interface with a microcontroller or other digital circuitry.

🤔SHIFT REGISTER

⚡The 74HC595 is a shift register with output latches, and its function block can be divided into three main parts: the shift register, the storage register (latch), and the output drivers.

  1. 💫Shift Register: The shift register section of the 74HC595 is responsible for receiving and storing data in a serial-in, parallel-out manner. The input data is shifted through the register one bit at a time upon receiving clock pulses. The data enters through the serial data input pin (SER) and moves through the shift register on each clock cycle. This allows multiple bits of data to be sequentially loaded and stored.
  2. 💫Storage Register (Latch): The storage register, or latch, is the part of the 74HC595 that holds the data after it has been shifted through the shift register. The shift register's content can be transferred to the latch by activating the latch enable (SRCLK) pin. This ensures that the data remains stable and unchanged until the latch enable signal is received.
  3. 💫Output Drivers: The output section of the 74HC595 consists of eight output pins (QA-QH), which correspond to the eight bits of data stored in the shift register and latch. These pins drive the connected external components, such as LEDs, based on the stored data. The outputs of the 74HC595 are usually connected to current-limiting resistors and then to the desired external components or devices.

  • 🔥When the input OE is high, the output QA-QH is disabled regardless of other input states。
  • 🔥When the input OE is low, the output QA-QH is enabled regardless of other input states。
  • 🔥When the input SRCLR is low, set the shift register to 0。
  • 🔥When entering SRCLR at a high level, SER at a low level, SRCLK at a rising edge, the first level of the shift register gets lower, and the other levels store the previous level of data separately。
  • 🔥When the input SRCLR is high, the SER input is high, the SRCLK input is a rising edge, the first level of the shift register is high, and the other levels store the previous level of data separately。
  • 🔥When the input RCLK has a rising edge, the shift register data is stored in a storage register, regardless of other input states。

🤔APPLICATION

⚡LED Driver

🔌note

  • 💥Load current, each output should not exceed 35mA, total output 70mA
  • 💥Output voltage, output should not be pulled over the VCC

🔌Output voltage and current

 
74HC595
Input Voltage Vcc 5V
Output Voltage VO 5V
LED
Forward Voltage VF 2.5V
Forward Current IF 20mA
  • 💥Resistance and LED composed of a series circuit, Ohm's law, resistance on the current IR：is 5.3mA。