### Technical Overview of LD1985-28-AF5-R The **LD1985-28-AF5-R** is a high-performance, low-dropout (LDO) linear voltage regulator manufactured by UTC (Unisonic Technologies). It is designed specifically for applications requiring low noise, high precision, and low power consumption, such as battery-operated portable devices. --- ### 1. Key Technical Specifications | Parameter | Value | Description | | :--- | :--- | :--- | | **Output Voltage** | 2.8V | Fixed output voltage level. | | **Output Current** | 150mA | Maximum continuous current delivery. | | **Dropout Voltage** | 100mV (typ) | Voltage drop at 100mA load. | | **Input Voltage Range** | Up to 16V | Maximum allowable input supply voltage. | | **Package Type** | SOT-25 / SOT-23-5 | Small footprint surface mount package. | | **Quiescent Current** | 80µA | Current consumed by the IC at no load. | | **PSRR** | 70dB | Power Supply Rejection Ratio at 1kHz. | --- ### 2. Pin Configuration (SOT-25) The device typically utilizes a 5-pin configuration to allow for control and stability: 1. **VIN**: Input Voltage Supply. 2. **GND**: Ground Reference. 3. **ON/OFF (Enable)**: Logic-level input to turn the regulator on or off. High = On, Low = Shutdown. 4. **BYPASS**: Pin for an external capacitor to reduce noise and improve stability. 5. **VOUT**: Regulated Output Voltage (2.8V). --- ### 3. Core Features and Protection * **Low Noise Operation:** By adding an external capacitor to the Bypass pin, the output noise is significantly reduced, making it ideal for RF and sensitive analog circuits. * **Internal Protection:** * **Current Limiting:** Protects the IC during short-circuit or overload conditions. * **Thermal Shutdown:** Automatically shuts off the device if the junction temperature exceeds safe limits (typically around 150°C). * **Low Shutdown Current:** In "Off" mode, the device draws less than 1µA, preserving battery life. --- ### 4. Typical Application Circuit To ensure stability and performance, external capacitors are required: ```c [Input Voltage] ----+---- [VIN] [VOUT] ----+---- [2.8V Output] | | [Cin: 1uF] [Cout: 2.2uF] | | [GND] [GND] ``` --- ### 5. Ordering Information Decoded * **LD1985**: Part Series (LDO Regulator). * **28**: Output Voltage (2.8 Volts). * **AF5**: Package code for SOT-25. * **R**: Tape and Reel packaging.