The **LD2985G-C3-AF5-R** is a low-dropout (LDO) linear voltage regulator manufactured by UTC (Unisonic Technologies). It is designed for battery-powered applications where low noise, low dropout voltage, and low quiescent current are critical. --- ## 1. Component Overview The device provides a stable fixed output voltage from a higher input voltage. It includes an internal P-channel MOSFET pass transistor, which allows it to maintain regulation even when the input voltage is only slightly higher than the output. ### Key Specifications | Parameter | Specification | | :--- | :--- | | **Output Voltage (Fixed)** | 3.3V (indicated by the "C3" code) | | **Output Current** | 150mA (Maximum) | | **Dropout Voltage** | ~160mV @ 50mA / ~300mV @ 150mA | | **Input Voltage Range** | Up to 16V | | **Package Type** | SOT-25 (also known as SOT-23-5) | | **Operating Temperature** | -40°C to +125°C | --- ## 2. Pin Configuration (SOT-25) This component typically uses a 5-pin layout to provide control and noise reduction. | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **VIN** | Input Supply Voltage | | 2 | **GND** | Ground | | 3 | **ON/OFF** | Shutdown Control (High = Active, Low = Off) | | 4 | **BYPASS** | Connection for an external capacitor to reduce noise | | 5 | **VOUT** | Regulated Output Voltage | --- ## 3. Part Number Decoder Breaking down the nomenclature of **LD2985G-C3-AF5-R**: * **LD2985**: Basic Part Number (LDO Regulator). * **G**: Halogen-free and RoHS compliant. * **C3**: Represents the **3.3V** output voltage version. * **AF5**: Package code for **SOT-25**. * **R**: Tape and Reel packaging. --- ## 4. Key Electronic Features 1. **Low Noise:** By connecting a small capacitor to the **BYPASS** pin, high-frequency noise is filtered, making it suitable for RF and sensitive analog circuits. 2. **Logic-Controlled Shutdown:** The device can be turned off via a logic signal to conserve battery life (quiescent current drops to near zero). 3. **Protection Circuits:** It features internal thermal overload protection and short-circuit current limiting. 4. **Stability:** It is designed to be stable with low-ESR ceramic capacitors, saving board space compared to older regulators requiring tantalum capacitors. --- ## 5. Typical Application Circuit To use this part, you generally need three external capacitors: ```markdown VIN ----[ Cin (1uF) ]----+----[ PIN 1 ] | GND ---------------------+----[ PIN 2 ] | ON/OFF ------------------+----[ PIN 3 ] (Connect to VIN to enable) | BYPASS --[ Cbp (10nF) ]--+----[ PIN 4 ] (Optional for low noise) | VOUT ----[ Cout (2.2uF)]-+----[ PIN 5 ] ```