Sumida provides a range of Point of Load (POL) power modules for use in low voltage power conversion. Applications include communication and industrial products, servers, consumer products, test equipment, and distributed power systems.

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Technical Questions

What is a PSI2?
A PSI2 (Power Supply in Inductor) is a non-isolated buck (i.e. step-down) or boost (step-up) DC-DC switching power supply module with all components, including the semiconductor switches and controller, being integrated inside the inductor to form a single package.

What is the advantage of putting the components inside the inductor?
The inductor is the largest single component in any Point of Load (POL) power supply, and is one of the most critical components for performance and efficiency. By placing the other components inside the inductor, the volume available for the inductor can be made as large as possible. This allows the inductor losses to be reduced to a minimum, resulting in the best efficiency for the module. In addition, the magnetic material has a good thermal conductivity to avoid hot spots, and provides shielding to reduce noise and EMI.

Why use a module - why not use a discrete power converter solution?
By using a PSI2 module you shorten your system design time and reduce risk, because the module is fully tested. All high frequency circuits, stability and filtering components are internal to the module and you only have to make the DC connections for input and output. A recent industry study* has shown a reduction of about 40% in design time, as well as a substantial reduction in the number of design iterations needed to complete the design.

What is the main application of PSI2?
The Sumida PSI2 can be used in any system which needs to convert from an intermediate voltage to a high current, low voltage internally. The module can be used to provide up to 6A current to power ASICs and microprocessors on a system board used in an industrial controller, server, telecom or embedded system. For custom requirements, Sumida can design a PSI2 module with a different voltage or a higher output current (up to 12A or higher).

What is inside a PSI2?
Sumida PSI2 incorporates a switching controller with two power MOSFETs (one being used as a synchronous rectifier), a power inductor, an input capacitor and an output capacitor together with supporting components.

Do I need to install other external components for my PSI2?
Although input and output capacitors are integrated into our PSI2, we recommend using a 100uF (ceramic) external input capacitor and a 200uF (ceramic) external output capacitor for decoupling, mounted as close to the PSI2 as possible.

Why do I need high efficiency?
High efficiency is needed for two main reasons: to save energy, and to reduce temperature rise. The cost of energy is continually rising and has been estimated to cost as much as $13/watt over the life of a product. In a system with backup power (DC telecom system, or datacenter with UPS backup) the total cost can be as high as $20/watt including all costs involved. By saving 1W of power consumption in this type of equipment you are saving the end user $20 over the lifetime of his system, a very attractive selling point. Reducing the temperature rise not only improves system reliability but also reduces the need for air conditioning, further reducing the energy consumption.

Does Sumida PSI2 support Sequencing Operation?
Yes, the Sumida PSI2 has a control pin for 'Power Good' (output) and 'Enable' (input). If you want to turn on two (or more) PSI2 modules in sequence, you can connect the 'Power Good' pin of the first module to the 'Enable' pin of the second module. By doing so, the second module will only be turned on after the first module voltage has risen to its normal set-point.

Why does the output voltage of my PSI2 drop when the output current is increased?
This is because of voltage drop in the PCB power and ground traces on your board, and is called 'load regulation'. You can improve the load regulation by improving your printed circuit board (PCB) layout to reduce track length and increase width, and by connecting the 'Voltage Sense' pin of the PSI2 as close to the load as possible.

Can this device be supplied in a different package?
The Land Grid Array (LGA) package used currently offers a number of advantages, both electrically and thermally, and is our preferred package. However, we can consider different package options for a custom application.

Can Sumida offer custom products?
Yes, Sumida is customer focused and will consider any custom requirement for high volume applications. Please contact us at to discuss your application

* Darnell white paper, 240412 Ease of Design Comparison (April 2012)
The paper can be downloaded at