The **78R00L-TF4-R** is a specific low-dropout (LDO) voltage regulator manufactured by UTC (Unisonic Technologies Co., Ltd). It belongs to the "78R" family, which are essentially positive voltage regulators with an added **ON/OFF control** pin. --- ### 1. General Specifications The "00" in the part number indicates that this is an **adjustable** version, allowing the user to set the output voltage via external resistors. | Parameter | Specification | | :--- | :--- | | **Type** | Low Dropout (LDO) Voltage Regulator | | **Output Type** | Adjustable (ADJ) | | **Output Current** | 1.0 A (Maximum) | | **Dropout Voltage** | ~0.5V at 1A | | **Package Type** | TO-220F-4 (Full-mold, 4 pins) | | **Control Function** | Built-in ON/OFF Control Pin | --- ### 2. Pin Configuration The "TF4" suffix indicates the 4-pin layout (unlike standard 3-pin 78xx regulators). | Pin Number | Symbol | Function | | :---: | :--- | :--- | | 1 | **Vin** | Unregulated DC Input Voltage | | 2 | **Vout** | Regulated Output Voltage | | 3 | **GND/ADJ** | Ground / Feedback Adjustment | | 4 | **Vcont** | ON/OFF Control (High = ON, Low = OFF) | --- ### 3. Key Features and Protections * **ON/OFF Control:** This is the defining feature. It allows the power supply to be toggled electronically by a microcontroller or logic circuit without physical switches. * **Low Dropout Voltage:** Requires a very small difference between input and output voltage to function properly (useful for battery efficiency). * **Over-Current Protection:** Limits output current to prevent damage during a short circuit. * **Thermal Shutdown:** Automatically turns off if the internal chip temperature becomes too high. --- ### 4. Part Number Decoding Understanding the nomenclature helps in identifying equivalent parts: * **78R**: Series (Regulator with control pin) * **00**: Adjustable voltage (If it were "05", it would be fixed 5V) * **L**: Lead-free (Halogen-free) * **TF4**: Package code (TO-220F-4) * **R**: Tape and Reel or specific packing code --- ### 5. Simple Application Circuit To use the adjustable feature, you typically use a voltage divider at Pin 3. ```text [Vin] ----+----[ 78R00L ]----+---- [Vout] | Pin 4 (Ctl) | | | +----[R1]----+ [Cin] [MCU] | | +----[R2]----+ | | | [GND] ----+------------------+------------+ ``` ---