When Should You Use a Power Module vs. PMIC?

Everyone likes to have PCBs with devices that have low noise, small footprint, and thermal efficiency. Unfortunately with power electronics, you can usually only achieve 2 out of 3 of those points in the previous sentence. The power supply and regulator module options on the market tend to do well in at least one of those areas, but sometimes for a high price tag for such a high value add component.

If you’re designing your own power regulator circuitry for modern embedded systems, then you most likely will prioritize small footprint over other aspects of a design. Small footprint and thermal/power efficiency might be available in some power modules, which can operate at standard voltages and moderately high power. So should you use these systems in your design? We’ll examine this by comparing power regulator module capabilities with typical features found in PMICs.

When to Use Power Regulator Modules

PMICs have been the go-to solution for power regulator design for a long time, and they will continue to be useful solutions in many cases. PMICs are like any other IC; they provide an integrated platform with multiple features in a single component, but they do not pack all the components into a single package. Many PMICs will place the main control circuitry on the die, while externally you would be required to include bulk capacitance, inductance, and even switching FETs.

Power modules take a somewhat different approach. Rather than implementing only the oscillator, switcher, and maybe isolation, power regulator modules aim to place as much of the power supply circuit as possible into a single package. Power modules are designed with an attempt to include everything needed to ensure stability in the power system, including:

• Integrated inductor
• Switching FETs
• Transformer for isolation
• Feedback and control loop
• Additional control (thermal monitoring, current limiting, etc.)

These parts follow two trends in component design: heterogeneous integration and miniaturization. The FETs, inductances, and control loops may be packaged on an organic substrate, just like an advanced processor package. In this case, the power module could require an LGA or BGA footprint on the PCB. These components could also be placed on a single die and packaged in, for example, a QFN package. An example LGA-like footprint for a small fixed-output power module is shown below.

This example LGA pattern allows for high current handling, low-impedance ground connections, and easy access to control pins on the module.

PMIC or Power Module?

Just from looking at the component size, power modules look like they have some advantages over PMICs and one might wonder why power modules are not used more often. It is true that power modules offer a real footprint advantage and they can be easier to drop into existing designs, but as of 2023 they do not cover all possible application areas. The table below gives a comparison of PMICs vs. power modules.

From this table we have some important points to consider when using PMICs:

• They generally require more external components, but this is needed to reach higher power output values
• PMICs area available to support any topology, including designs like flyback converters that pull power from mains
• PMIC chips can be much lower cost than a comparable module, and they are available from multiple manufacturers
• Although external components (caps and inductive elements) are needed with PMICs, your design may have lower noise (EMI)

So which systems are making more use of power modules? Power supplies for embedded systems, wearable devices, IoT/home, and some automotive products are all candidates for power modules. PMICs still dominate higher power areas like lighting, AC/DC conversion, electric vehicles, and industrial equipment.

Summary

If your goal is to have a power regulator with a very small footprint that does not require extreme design effort, then a power module is a good solution. If the goal is to use a standard topology at higher power outputs, PMICs are still a good choice. Power module capabilities should only be expected to expand as more semiconductor manufacturers start to produce module versions of their popular PMICs.

When you’re designing power products and you need to evaluate circuit performance, use the complete set of system analysis tools from Cadence to evaluate systems functionality. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity. Cadence PCB design products also integrate with a multiphysics field solver for thermal analysis, including verification of thermally sensitive chip and package designs.

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