The **U74AHC595G-R16-R** is a high-speed CMOS device, specifically an **8-bit serial-in, serial or parallel-out shift register with output latches and 3-state outputs**. It is widely used in digital electronics to expand the number of output pins on a microcontroller (GPIO expansion). --- ### 1. Key Technical Specifications | Parameter | Description | | :--- | :--- | | **Logic Family** | AHC (Advanced High-Speed CMOS) | | **Function** | 8-Bit Shift Register with 3-State Output | | **Operating Voltage ($V_{CC}$)** | 2.0V to 5.5V | | **Propagation Delay** | Approx. 3.5ns to 5ns (at 5V) | | **Output Current** | ±8.0 mA | | **Package Type** | SOP-16 / TSSOP-16 (R16 suffix denotes package size) | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Functional Components The device consists of two primary internal stages: 1. **8-Bit Shift Register:** Receives data serially through the `DS` (Data Serial) pin on every positive transition of the Shift Clock (`SHCP`). 2. **8-Bit Storage Register (Latch):** When the Storage Clock (`STCP`) is pulsed, the data from the shift register is transferred to the storage register, which drives the output pins ($Q_0$ to $Q_7$). --- ### 3. Pinout Description | Pin Name | Type | Function | | :--- | :--- | :--- | | **DS** | Input | Serial Data Input | | **SHCP** | Input | Shift Register Clock Input | | **STCP** | Input | Storage Register Clock Input (Latch) | | **$\overline{OE}$** | Input | Output Enable (Active Low) | | **$\overline{MR}$** | Input | Master Reset (Active Low) | | **$Q_0 - Q_7$** | Output | Parallel Data Outputs | | **$Q_7'$** | Output | Serial Data Output (for cascading multiple ICs) | --- ### 4. Code Implementation Example (Arduino) To control this IC, the `shiftOut()` function is typically used. ```cpp int latchPin = 8; // STCP int clockPin = 12; // SHCP int dataPin = 11; // DS void setup() { pinMode(latchPin, OUTPUT); pinMode(clockPin, OUTPUT); pinMode(dataPin, OUTPUT); } void loop() { digitalWrite(latchPin, LOW); // Shift out the bits (Binary: 10101010) shiftOut(dataPin, clockPin, MSBFIRST, 0b10101010); digitalWrite(latchPin, HIGH); delay(1000); } ``` --- ### 5. Common Applications * **LED Driving:** Controlling 7-segment displays or LED matrices using only 3 MCU pins. * **IO Expansion:** Adding more digital outputs to microcontrollers like Arduino, ESP32, or STM32. * **Data Conversion:** Serial-to-parallel data conversion.