The **LD1985-2J-AF5-R** is a specific low-dropout (LDO) linear voltage regulator manufactured by **UTC (Unisonic Technologies)**. It is designed for battery-powered applications where low noise and low ground current are essential. --- ## 1. Technical Specifications Below are the primary electronic characteristics of the LD1985-2J-AF5-R: | Parameter | Value | | :--- | :--- | | **Output Voltage** | 2.85V (Fixed) | | **Input Voltage Range** | Up to 16V (Max) | | **Output Current** | 150mA | | **Dropout Voltage** | Typically 300mV @ 150mA | | **Package Type** | SOT-25 / SOT-23-5 | | **Quiescent Current** | ~850µA (at full load) | | **Operating Temperature** | -40°C to +125°C | --- ## 2. Part Number Breakdown Understanding the nomenclature helps in identifying the exact variant: * **LD1985**: Basic series name (High accuracy, low-noise LDO). * **2J**: Indicates the output voltage code. In UTC’s naming convention, **2J** corresponds to **2.85V**. * **AF5**: Refers to the package type (**SOT-25** / **SOT-23-5**). * **R**: Indicates the packing method (**Tape and Reel**). --- ## 3. Pin Configuration (SOT-25) The device typically follows a standard 5-pin layout: 1. **V_IN**: Input Voltage. 2. **GND**: Ground. 3. **ON/OFF**: Control Pin (High = Enabled, Low = Shutdown). 4. **BYPASS**: Noise bypass pin (Connecting a small capacitor here reduces output noise). 5. **V_OUT**: Regulated Output Voltage (2.85V). --- ## 4. Key Electronic Features ### A. Low Dropout Voltage The device can maintain a stable 2.85V output even when the input voltage is only slightly higher (approx. 3.15V). This is critical for maximizing battery life. ### B. Shutdown Mode The "ON/OFF" control pin allows the device to enter a zero-current mode, effectively drawing less than 1µA when the circuit is inactive. ### C. Low Noise Operation By utilizing the Bypass pin with a capacitor, the internal reference voltage is filtered, providing a very "clean" DC output suitable for sensitive RF or audio components. ### D. Built-in Protections * **Current Limiting**: Protects the chip during output shorts. * **Thermal Shutdown**: Turns off the regulator if the internal die temperature exceeds safe limits (approx. 150°C). --- ## 5. Typical Application Circuit ```text Vin ----+-------[ IN ]-------[ OUT ]-------+---- Vout (2.85V) | [ LD1985 ] | C_in [ SHDN ] C_out | | | GND MCU/Switch GND ```