Miniaturization is an eternal topic in the electronics industry, and power supplies are no exception. The quality of a power supply can be expressed in terms of power per unit volume. This article introduces methods to reduce size when designing power supplies.


■ Minimizing the number of external parts

A power supply consists of at least one semiconductor and external passive components such as inductors, capacitors, and several resistors. The first step to reducing the overall size of the power supply is to reduce the number of external components, as shown in Figure 1.

When features such as the ability to adjust the output voltage or the soft start time are required, the number of passive components will increase, and as a result, the overall space occupied by the solution will increase. The circuit in Figure 1 shows a switch-mode buck converter using minimal passive components.





■ Minimizing the size of external components

To minimize the size of the output capacitor and inductor, the switching regulator IC must use the highest possible switching frequency. The voltage ripple of the output voltage operates linearly according to the values of the external components and their corresponding magnitude.

For example, doubling the switching frequency can reduce the required inductance value for the same output voltage ripple by half. This allows for a more compact design. Figure 2 shows the area required by the LTC3307A switching regulator. Since the switching frequency is high at 3 MHz, a small inductor can be used.





■ Minimizing the size of switching regulator ICs

Analog Devices' LTC33xx platform includes switch-mode step-down voltage converter products that operate at high switching frequencies up to 5 MHz for use in a variety of applications.

The LTC3315A is suitable for use in space-constrained applications. As a 2-channel dual converter provided in a 1.64mm x 1.64mm WLCSP (wafer-level chip scale package) package, it can provide 2A of output current per channel.

The MAX77324 is also a noteworthy product. The MAX77324 is a single-channel step-down switching regulator that provides a maximum output current of 1.5A in a 1.22mm x 0.85mm size. Figure 3 shows the package footprint of the MAX77324.





■ Miniaturization by integrating the inductor

Another way to reduce the size of a power supply circuit is to integrate the inductor and switching regulator ICs. This integrated unit is called a module.

The length of the solution can be reduced by placing the inductor on top of the semiconductor IC. Miniaturization can be achieved by using the inductor integrated into the module as a thermal conductor and heat sink. By properly connecting the inductor to the silicon within the module, heat can be effectively removed from the semiconductor.

In particular, heat dissipation is becoming an increasingly significant issue when providing high output currents in small switching regulator ICs. This is because silicon cannot operate above its maximum allowable operating temperature.

In addition to these, there are various innovative ways to reduce the size of power supplies, but this article has only examined a few of them. Miniaturization also offers other indirect benefits. It reduces costs by occupying less board space, enhances device functionality, and enables lower transportation costs by reducing the size and weight of electronic equipment.

※ Author Introduction
Frederik Dostal majored in microelectronics at the University of Erlangen in Germany. He began his career in power management in 2001 and gained experience in various applications, including working with switch-mode power supplies in Phoenix, Arizona for four years. He joined Analog Devices in 2009 and currently serves as a Power Management Field Application Engineer (FAE) at the ADI Munich office.