The **78R05L-TF4-R** is a specific low-dropout (LDO) voltage regulator part, commonly manufactured by Unisonic Technologies (UTC). It belongs to the 78xx family but includes a specific feature: a **built-in ON/OFF control terminal**. --- ### 1. Key Technical Specifications Below are the primary electrical characteristics of the 78R05L-TF4-R: | Parameter | Specification | | :--- | :--- | | **Output Voltage** | +5V DC | | **Input Voltage Range** | Up to 15V (Typical Operating) | | **Output Current** | 1.0 Ampere | | **Dropout Voltage** | Low Dropout (approx. 0.5V at 1A) | | **Package Type** | TO-220F-4L (Full-mold 4-pin) | | **Control Pin** | High-level ON / Low-level OFF | --- ### 2. Pin Configuration Unlike the standard 3-pin 7805 regulator, this part features **4 pins**. The extra pin allows for digital control of the power output. 1. **V_IN**: Input Voltage. 2. **V_OUT**: Regulated 5V Output. 3. **GND**: Ground. 4. **V_CONT (Control)**: Enables or disables the regulator. --- ### 3. Core Features & Functions * **LDO (Low Dropout):** This allows the device to maintain a stable 5V output even when the input voltage is only slightly higher than 5V (e.g., 5.5V). This is more efficient than standard 7805 regulators. * **ON/OFF Control:** By applying a signal to the 4th pin, you can turn off the 5V output. This is essential for power-saving modes in microcontrollers or battery-powered devices. * **Protection Circuits:** * **Over-current protection:** Limits current if the load exceeds 1A. * **Thermal shutdown:** Automatically shuts off if the chip becomes too hot. * **TF4-R Nomenclature:** * **TF4:** Refers to the TO-220F-4L package (the "F" stands for Full-mold, meaning the tab is insulated). * **R:** Usually indicates Tape & Reel or specific RoHS compliance/packaging standards. --- ### 4. Typical Application Circuit When wiring the 78R05L-TF4-R, you typically need two capacitors to ensure stability: ```text Input (7V-15V) ---[ 0.33uF Cap ]--- PIN 1 (VIN) PIN 2 (VOUT) ---[ 10uF Cap ]--- Output (5V) PIN 3 (GND) ------------------ Ground Control Signal (0/5V) ------------- PIN 4 (CONT) ```