The **78DXXL-TM3-R** is a series of three-terminal medium current positive voltage regulators. It is a surface-mount version of the classic 78xx series, designed to provide a stable fixed output voltage from a fluctuating DC input. ### 1. Part Number Breakdown Understanding the nomenclature helps identify the specific characteristics of the component: | Component Segment | Meaning | | :--- | :--- | | **78D** | 78 Series (Positive Voltage Regulator) / **D** denotes 500mA output current | | **XX** | Voltage Code (e.g., 05 = 5V, 12 = 12V) | | **L** | Lead-free / RoHS compliant | | **TM3** | Package Code (typically refers to TO-252 / D-PAK) | | **R** | Packing method (Tape & Reel) | --- ### 2. Key Technical Specifications While specific values depend on the "XX" voltage rating, the general characteristics for the series are: * **Output Current:** Up to 500mA. * **Input Voltage Range:** Usually up to 35V (depending on output voltage). * **Protection Features:** * Internal Thermal Overload Protection. * Short Circuit Current Limiting. * Output Transistor Safe Area Protection. * **Operating Temperature:** Typically -40°C to +125°C. --- ### 3. Pin Configuration (TO-252 / TM3) The device usually follows the standard layout for D-PAK voltage regulators: | Pin Number | Function | Description | | :--- | :--- | :--- | | 1 | **Input** | Unregulated DC voltage input | | 2 / Tab | **GND** | Ground connection (Tab is also GND for heat dissipation) | | 3 | **Output** | Regulated fixed DC voltage output | --- ### 4. Typical Application Circuit To ensure stability and reduce noise, external capacitors are required. ```markdown Vin ----[ 1: IN ]----------[ 3: OUT ]---- Vout | | | [C1] [GND] [C2] | | | GND ---------------------------- Ground ``` * **C1 (Input Capacitor):** 0.33µF (Ceramic or Tantalum) to compensate for line inductance. * **C2 (Output Capacitor):** 0.1µF to improve transient response and stability. --- ### 5. Heat Dissipation Warning Because this is a **Linear Regulator**, it drops excess voltage as heat. The formula for power dissipation is: `P = (Vin - Vout) × Iout` If the temperature exceeds limits, the "Thermal Overload Protection" will shut the device down. Since the **TM3 (TO-252)** package is a surface-mount part, the copper area on the PCB acts as the primary heatsink.