The **LDK220M-R** is a low-dropout (LDO) linear voltage regulator designed by STMicroelectronics. It is specifically engineered for low-noise performance and high-accuracy voltage regulation in battery-powered and space-constrained applications. --- ## 1. Technical Specifications The following table outlines the primary electrical characteristics of the LDK220M-R: | Parameter | Specification | | :--- | :--- | | **Output Type** | Fixed (R suffix indicates a specific voltage) | | **Output Voltage ($V_{out}$)** | 1.2V to 12V (Model dependent) | | **Input Voltage ($V_{in}$)** | 2.5V to 13.2V | | **Max Output Current** | 200 mA | | **Dropout Voltage** | 100 mV @ 100 mA load | | **Quiescent Current ($I_q$)** | 55 µA (typ.) | | **PSRR** | 60 dB @ 1 kHz | | **Package** | SOT-23-5L | --- ## 2. Key Internal Components The LDK220M-R is an integrated circuit (IC) that contains several critical sub-systems to manage power: ### A. Pass Transistor The heart of the LDO is a **P-channel MOSFET**. Unlike N-channel regulators, the P-channel architecture allows for a very low dropout voltage, meaning the input voltage only needs to be slightly higher than the target output voltage for the device to function. ### B. Error Amplifier This component constantly compares the feedback voltage from the output against an internal **Bandgap Reference**. If the output voltage drops, the error amplifier adjusts the gate of the MOSFET to allow more current through. ### C. Protection Circuitry The device includes three main safety features: * **Current Limit:** Prevents the device from burning out if the output is short-circuited. * **Thermal Shutdown:** Automatically turns off the regulator if the internal temperature exceeds a safe threshold (typically ~160°C). * **Enable Pin (EN):** Allows the regulator to be put into a low-power "Shutdown Mode" (drawing less than 1 µA). --- ## 3. Pin Configuration (SOT-23-5) The LDK220M-R uses a standard 5-pin layout: 1. **IN:** Input voltage supply. 2. **GND:** Ground. 3. **EN:** Enable control (High = On, Low = Off). 4. **NC/ADJ:** No connection (for fixed versions) or adjustment pin. 5. **OUT:** Regulated output voltage. --- ## 4. Typical Application Circuit To ensure stability, the LDK220M-R requires external ceramic capacitors. ```mermaid graph LR Vin(Input Voltage) -->|1uF Cap| IN[LDK220 Pin 1] IN --> OUT[LDK220 Pin 5] OUT -->|1uF Cap| Vout(Stable Output) EN[Pin 3] --> Logic(MCU Control) GND[Pin 2] --- Earth(Ground) ``` ### Capacitor Requirements * **Input Capacitor:** 1 µF ceramic is recommended to minimize input impedance. * **Output Capacitor:** 1 µF ceramic (minimum) is required for loop stability. The LDK220 is specifically designed to be stable with **low ESR** ceramic capacitors.