Power modules have been available on the market for many years. They are single-package products, typically switch-mode power supplies (SMPS), that can be simply soldered onto a board and convert an input voltage to a specific output voltage.

Unlike switching regulator ICs, which integrate only the controller and power switches on the chip, power modules integrate a number of passive components.

The term 'power module' is generally used when an inductor is integrated.

Figure 2 shows the components required for a switch-mode step-down converter (buck topology). The dotted line in the figure distinguishes the switching regulator IC from the power module. Since the voltage conversion circuit for these modules is developed by the power module company, users do not need to be power supply experts.

There is another advantage. The high level of integration of this module allows for extremely small size of the SMPS.

■ Implementing quieter and smaller DC-DC regulation

Switching regulators inherently generate radiated EMI because they operate at relatively high frequencies and with high dI/dt. EMI compliance is a mandatory requirement and a critical design challenge for signal processing in medical equipment, RF transceivers, and test and measurement systems.

For example, if a system fails to meet EMI requirements, or if a switching regulator impacts high-speed digital or RF signal integrity, debugging or design changes will not only lengthen the design schedule but also increase costs due to revalidation. Moreover, in dense PCB layouts where DC-DC switching regulators are placed close to noise-sensitive components or signal wiring, the potential for noise generation can be more pronounced.

Instead of using cumbersome EMI mitigation techniques such as lowering the switching frequency, adding filter circuits to the PCB, and shielding, a better approach is to suppress the noise at its source: the DC-DC semiconductor itself.

For a more compact DC-DC solution, all components, including MOSFETs, inductors, DC-DC ICs, and support components, can be integrated into an extremely small overmolded package in the form of a surface-mount IC (Figure 1).

In addition to quieter DC-DC conversion and a small footprint that meets most EMI compliance requirements such as EN 55022 Class B, it is also important to minimize the number of external components such as output capacitors on the PCB.

A DC-DC regulator with a fast transient response can reduce its dependence on output capacitance.

This simplifies the design due to the optimized internal feedback loop compensation, which allows the use of different types of output capacitors over a wide range of operating conditions and provides sufficient stability margin.

The LTM8074 is a 1.2A, 40VIN micromodule (μModule) step-down regulator housed in a tiny 4mm x 4mm x 1.82mm BGA package with a 0.65mm pitch. The overall solution size is 60㎟ for 3.2VIN to 40VIN, 3.3VOUT, and requires only two 0805 capacitors and two 0603 resistors.

Additionally, the low package height and light weight (0.08 grams) allow the device to be mounted on the bottom of a PCB when other components are densely packed on the top. Furthermore, the LTM8074's Silent Switcher architecture minimizes EMI emissions, allowing it to comfortably meet CISPR22 Class B requirements and reduce the EMC vulnerability of other sensitive circuits.

Integrating all external components is impossible. The reason is simple: for example, to enable adjustable settings like switching frequency or soft-start time, you need to tell the circuit what to do.

This can be done digitally. This requires the use of microcontrollers and non-volatile memory, which increases system cost.

A common way to avoid this is to use external passive components to enable these settings.

Input and output capacitors are often integrated into the power module, but sometimes they may be required externally. Figure 4 shows a circuit using the LTM8074 from Analog Devices.
The ability to set the desired output voltage using only a single external resistor reduces the number of product models and provides a degree of application flexibility. When soft-start functionality is not required, no capacitor is required on the pin. All of these features enable voltage conversion to be implemented in an extremely small board area.

The LTM8074 measures just 4mm x 4mm and requires minimal external wiring, enabling a complete power supply capable of up to 40V input voltage and up to 1.2A of allowable output current to be implemented in a board area of only about 8mm x 8mm. Figure 5 shows the result of a layout using only the minimum number of external components.
For small power supplies, very high conversion efficiency is crucial, otherwise heat dissipation problems may occur.

The new, ultra-small LTM8074 is an ideal choice for this purpose. Thanks to its Silent Switcher technology, it's ideal for use in circuits particularly sensitive to noise, typically requiring linear regulators.

Highly integrated power modules not only simplify SMPS design, but are also suitable for achieving efficient voltage conversion in a very small space.

The performance characteristics of ADI Module devices can be summarized as follows:
- Lower noise (ultra-low noise and silent switcher devices)
- Ultra-thin package
- Efficient cooling across 6 sides (CoP)
- Precise VOUT regulation over line, load, and temperature
- Extreme reliability testing
- Minimize ground loops
- Multiple outputs available
- Extreme temperature testing

※ About the author
Frederik Dostal, FAE / Analog Devices, Inc.

Frederik Dostal studied microelectronics at the University of Erlangen in Nuremberg, Germany. He began his career in power management in 2001 and held various application positions, including four years working on switch-mode power supplies (SMPS) in Phoenix, Arizona. He joined Analog Devices in 2009 and currently serves as a Power Management Field Application Engineer (FAE) in ADI's Munich office.