The **ADP2138ACBZ-2.5-R7** is a high-efficiency, low quiescent current, step-down (buck) DC-to-DC converter manufactured by Analog Devices. It is specifically designed for portable applications where board space and battery life are critical. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Output Voltage** | 2.5 V (Fixed) | | **Input Voltage Range** | 2.3 V to 5.5 V | | **Continuous Output Current** | 800 mA | | **Switching Frequency** | 3.0 MHz | | **Package Type** | WLCSP (Wafer Level Chip Scale Package) | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Core Features * **High Efficiency:** Uses synchronous rectification to achieve efficiency levels up to 95%, reducing heat and preserving battery life. * **High Switching Frequency:** The 3.0 MHz frequency allows for the use of tiny, low-profile inductors and ceramic capacitors, minimizing the total PCB footprint. * **Internal Compensation:** The device is internally compensated, which simplifies the design process by reducing the number of required external components. * **Automatic Mode Switching:** Transitions automatically between **PWM** (Pulse Width Modulation) for high loads and **PSM** (Power Save Mode) for light loads to maximize efficiency across the entire current range. * **Protection Circuitry:** Includes undervoltage lockout (UVLO), soft start, thermal shutdown, and short-circuit protection. --- ### 3. Pin Configuration (WLCSP) Since this part uses a Ball Grid Array style package, the pinout is compact: | Pin Name | Function | | :--- | :--- | | **VIN** | Input power supply connection. | | **VOUT** | Output voltage sense and feedback input. | | **SW** | Switching node connection to the inductor. | | **GND** | Ground reference. | | **EN** | Enable input. High = On, Low = Shutdown. | --- ### 4. Typical Application Circuit To implement this part, you generally only need three external components: ```text Input (2.3V-5.5V) ----[ Cin ]----+----( VIN ) | [ADP2138]----( SW )----[ Inductor ]----+---- Output (2.5V) | | (GND)----------------------------[ Cout ]----( GND ) ``` * **Inductor:** Typically 1.0 µH. * **Input Capacitor (Cin):** Typically 4.7 µF ceramic. * **Output Capacitor (Cout):** Typically 10 µF ceramic. --- ### 5. Part Number Breakdown: `ADP2138ACBZ-2.5-R7` * **ADP2138:** Base model number. * **A:** Performance/Revision grade. * **CB:** Package code for WLCSP. * **Z:** RoHS compliant (Lead-free). * **2.5:** Fixed output voltage of 2.5 Volts. * **R7:** Packaging format (7-inch reel, typically 3,000 units).