SN74HC595PWR Detailed explanation of pin function specifications and circuit principle instructions
The SN74HC595PWR is a product of Texas Instruments, specifically a part of the 74HC595 family of serial-in, parallel-out shift registers. This component belongs to the 74HC (High-Speed CMOS) series, which is widely used for general-purpose logic applications. The PWR suffix indicates the packaging type, and the device comes in a TSSOP-16 package.
Key Features
It’s a Shift Register (Serial-In, Parallel-Out) that allows data to be shifted in bit by bit and outputs data in parallel. It is often used to expand I/O pins in systems (e.g., for controlling LED s, motors, etc.) by serially shifting data and converting it into parallel outputs.Pin Function Specification (TSSOP-16 Package)
The SN74HC595PWR has 16 pins, and here is the detailed explanation of each pin:
Pin Number Pin Name Function Description 1 QH’ Serial data output (Shift Register output). 2 QH Output pin for the parallel data shift register (bit 1 output). 3 Q7’ Output pin for the parallel data shift register (bit 2 output). 4 Q7 Output pin for the parallel data shift register (bit 3 output). 5 OE Output Enable (Active LOW). When LOW, it enables the output, otherwise, the output is disabled. 6 MR Master Reset (Active LOW). Resets the shift register to a defined state when LOW. 7 DS Data input pin (Serial Data Input). It receives the serial data. 8 SH_CP Shift Clock Pin (Clock input for shifting the data into the register). 9 ST_CP Latch Clock Pin (Clock for transferring the shifted data to the output latches). 10 Q0 Output pin for the parallel data shift register (bit 4 output). 11 Q1 Output pin for the parallel data shift register (bit 5 output). 12 Q2 Output pin for the parallel data shift register (bit 6 output). 13 Q3 Output pin for the parallel data shift register (bit 7 output). 14 Q4 Output pin for the parallel data shift register (bit 8 output). 15 Q5 Output pin for the parallel data shift register (bit 9 output). 16 VCC Power Supply Pin (Typically 5V). Provides power to the IC.Pin Function Explanation (Detailed)
QH’ (Pin 1): This is the Serial Output of the shift register, which sends out the serial data as the shift register is filled. QH (Pin 2): This is the Parallel Output (bit 1) for the data that is shifted into the register. It's part of the shift register’s output array. Q7’ (Pin 3): This pin is another Parallel Output and represents the shifted data output of bit 2. Q7 (Pin 4): Similar to Q7’, this pin outputs the shifted data from bit 3 of the register. OE (Pin 5): The Output Enable pin is used to enable or disable the outputs. When this pin is set to LOW, the outputs are enabled; otherwise, they are high-impedance. MR (Pin 6): This pin is used for a Master Reset. When LOW, it forces the shift register into a reset state, clearing the data. DS (Pin 7): The Serial Data Input is used to feed in data bit by bit to the shift register. SH_CP (Pin 8): This is the Shift Clock Pin. Each pulse on this pin shifts the data by one bit to the right. ST_CP (Pin 9): The Latch Clock Pin latches the shifted data and outputs it to the output pins when triggered. Q0 (Pin 10): This pin is one of the Parallel Outputs representing bit 4 of the shift register’s data. Q1 (Pin 11): Another Parallel Output for bit 5 of the register. Q2 (Pin 12): This pin is used for bit 6 output of the parallel data. Q3 (Pin 13): Represents bit 7 output from the shift register. Q4 (Pin 14): Another Parallel Output for bit 8 of the shift register. Q5 (Pin 15): Outputs bit 9 of the shift register’s data. VCC (Pin 16): This is the Power Supply Pin, which provides power to the IC. Typically, this is connected to a +5V source.FAQ on SN74HC595PWR Pin Functions (20 Common Questions)
Q: What is the function of the MR pin in SN74HC595PWR? A: The MR (Master Reset) pin clears the shift register, setting all outputs to 0 when it is LOW.
Q: What happens when the OE pin is set to HIGH? A: When the OE (Output Enable) pin is HIGH, the outputs are in a high-impedance state and cannot drive the connected load.
Q: Can the SHCP and STCP pins be connected to the same clock source? A: No, the SHCP pin controls the shifting, while the STCP pin controls latching the data. They need separate pulses for proper operation.
Q: How do I shift data into the SN74HC595PWR? A: Data is shifted into the device by applying clock pulses to the SH_CP (Shift Clock Pin) while sending serial data to the DS (Serial Data Input) pin.
Q: Can I connect the QH’ pin to another shift register? A: Yes, QH’ is the serial output, so it can be connected to the DS pin of another shift register for cascading.
Q: What happens if the VCC pin is not connected properly? A: Without proper power to the VCC pin, the IC will not function, and the outputs will remain in an undefined state.
Q: Is it necessary to connect the Q0 to Q7 pins for operation? A: No, it’s not necessary. You can use only the pins that are needed for your specific application.
Q: How do I initialize the shift register in SN74HC595PWR? A: Initialize the register by setting the MR pin LOW and then clocking in data via the DS and SH_CP pins.
Q: Can I use a microcontroller to control the SN74HC595PWR? A: Yes, you can use any microcontroller with SPI or GPIO pins to control the SN74HC595PWR.
Q: What is the maximum frequency for the SH_CP pin? A: The maximum frequency is typically 20 MHz for the SN74HC595PWR, but the actual speed depends on the supply voltage and load.
Q: Can I connect the OE pin to VCC? A: If you connect the OE pin to VCC, the outputs will always be in high-impedance mode, effectively disabling the outputs.
Q: What happens when the DS pin receives a LOW signal? A: A LOW signal on the DS pin shifts a 0 bit into the shift register.
Q: How does the STCP pin control the latch? A: The STCP pin triggers the latch to transfer the shifted data from the shift register to the output pins.
Q: Can the SN74HC595PWR be used to control LEDs? A: Yes, it is commonly used for controlling LEDs in a serial-to-parallel manner.
Q: How many shift registers can I daisy chain using QH’? A: You can cascade multiple SN74HC595PWR devices by connecting QH’ of one to the DS of the next for extended parallel output control.
Q: What is the voltage range for the SN74HC595PWR? A: The voltage range is typically between 2V and 6V, with 5V being the most common operating voltage.
Q: Does the SN74HC595PWR have built-in protection against over-voltage? A: No, the SN74HC595PWR does not have internal over-voltage protection; external protection circuitry should be used.
Q: What type of logic is supported by the SN74HC595PWR? A: The SN74HC595PWR supports CMOS logic, which is compatible with both TTL and CMOS logic levels.
Q: Can I control motors with the SN74HC595PWR? A: The SN74HC595PWR can control motors indirectly by driving transistor switches that control the motor power.
Q: What is the current rating for each output pin on the SN74HC595PWR? A: Each output pin can typically source or sink about 6 mA, so external transistors may be needed for high current applications.
This detailed breakdown ensures that all the pins and their functionality are fully understood for the SN74HC595PWR.
