## Technical Overview of ADP2503ACPZ-4.2-R7 The **ADP2503ACPZ-4.2-R7** is a high-efficiency, low quiescent current, step-up/step-down (buck-boost) DC-to-DC converter produced by Analog Devices. It is designed specifically for applications where the input voltage can vary above or below the required output voltage, such as single-cell Li-ion battery applications. ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Manufacturer** | Analog Devices Inc. | | **Topology** | Buck-Boost (Step-Up/Step-Down) | | **Output Voltage (Fixed)** | 4.2 V | | **Input Voltage Range** | 2.3 V to 5.5 V | | **Output Current** | Up to 600 mA | | **Switching Frequency** | 2.5 MHz | | **Package** | 10-LFCSP (3mm x 3mm) | | **Operating Temp** | -40°C to +125°C | --- ### 2. Core Functional Features * **Seamless Transitions:** The device uses a proprietary architecture that allows for a smooth transition between buck (step-down) and boost (step-up) modes without significant output voltage ripple or noise. * **High Switching Frequency:** Operating at 2.5 MHz allows for the use of tiny, low-profile inductors and ceramic capacitors, reducing the overall PCB footprint. * **Power Saving Mode (PSM):** At light loads, the converter can enter a power-saving mode to maintain high efficiency across the entire load range. * **Internal Compensation:** It features internal compensation and soft start to minimize the count of external components. --- ### 3. Pin Configuration (10-LFCSP) | Pin # | Name | Description | | :--- | :--- | :--- | | 1 | **VIN** | Input Voltage Source | | 2, 3 | **L1, L2** | Inductor Connection Pins | | 4 | **PGND** | Power Ground | | 5 | **VOUT** | Output Voltage | | 6 | **FB** | Feedback Input (Connected to VOUT for fixed versions) | | 7 | **GND** | Analog Ground | | 8 | **EN** | Enable Pin (High = On, Low = Shutdown) | | 9 | **SYNC/MODE** | Logic Input for PWM or Power Save Mode | --- ### 4. Application Context The 4.2V fixed output version is frequently used for: * **Battery Charging:** Providing a stable 4.2V rail for charging single-cell Lithium-ion/Polymer batteries. * **Handheld Devices:** Smartwatches, portable medical devices, and wireless sensors. * **USB Powered Gear:** Regulating 5V USB inputs down to a stable 4.2V rail even when the input fluctuates. ### 5. Part Number Breakdown `ADP2503` (Base Model) + `ACPZ` (Package Style) + `4.2` (Output Voltage) + `R7` (7-inch Reel Packaging). ---