A Compact Buck Converter Suitable For Wearables And IoT

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A buck converter is a DC-DC power device that efficiently steps down a voltage to a lower level. It uses an inductor, resistors, and a capacitor to regulate the output, making it particularly suitable for wearable electronics and IoT devices.

Low-dropout regulators (LDOs) offer a more straightforward approach to voltage regulation, but they often dissipate significant energy as heat, thereby undermining efficiency in compact, power-sensitive systems. Buck converters provide a more efficient solution, although the inclusion of an inductor increases the design footprint.

This compact converter design is based on a buck converter IC. The complete power system, including the converter, fits within a 9mm footprint—ideal for space-constrained applications while leaving room for other essential components.

A key feature is its ability to deliver variable output voltages ranging from 1.2V to 3.3V DC, achieved by replacing a fixed resistor with a potentiometer. This enables fine-tuned voltage adjustment to match the specific needs of each device.

The converter may be used as a standalone variable-voltage module or integrated directly into wearable electronics.

The converter is embedded within the device’s PCB, providing the desired output voltage range with over 93% efficiency and no thermal issues. The design incorporates the PAM2305D SMD IC, housed in a compact DFN-6 (2×2mm) package. Fig. 1 shows the author’s DC-DC buck converter integrated into the custom-designed PCB.

According to the datasheet of the IC selected for this converter design (for details, refer to the IC datasheet), the design requires an inductor, several resistors, and capacitors. If a variable output voltage is desired, a potentiometer can be used. The complete list of needed SMD components is provided in Table 1.

Design

The buck converter IC (PAM2305DGFADJ) comes with six pins. According to the application circuit in the datasheet, it includes a VIN pin for the input voltage, a GND pin for grounding, and an FB pin that receives feedback to regulate the output voltage. The EN (Enable) pin controls the IC’s operation when tied to a pull-up resistor or directly to the input voltage, enabling the IC to be active. When pulled low, it disables the converter. The SW (Switch) pin connects to an inductor, and the output voltage is set using two resistors configured between the SW, FB, and GND pins. Fig. 2 shows the IC (PAM2305DGFADJ) datasheet pinout and application circuit.