Drop-in Point of Load Modules: The Best in Class Power Solution

Electronics manufacturers must bring feature-rich, complex products to market on an increasingly aggressive time table. Electronics companies now view this as their predominant goal – and their most challenging pain point. The electronics design industry must improve product development efficiency in order to decrease time to market and reduce manufacturing costs – while building reliable, energy-efficient products. Manufacturers can now consider new power solution component choices that will help meet these requirements.

The Aberdeen Group published a report that identified the key criteria for consideration as a ‘Best in Class electronics manufacturer’. This group represents the top 20 percent of all manufacturers. These Best in Class manufacturers on average:

• Hit product development release dates 86% of the time
• Hit corporate revenue targets 88% of the time
• Met product development revenue costs with 88% accuracy
• Met product performance targets at 96%
• Hit product reliability targets with a 95% success rate.

All of these criteria and success rates can be directly affected, both negatively and positively, by the power solution design cycle and components selected.

Why modular POL?

The new breed of board-mounted, ‘drop-in’ Point of Load (POL) power solution is emerging as a proven, low-risk alternative to the legacy discrete POL solution. Not only do these ‘all-in-one’ POL modules speed up the power design cycle, but they also offer engineers a solution to the dilemma often created by the typical electronics design process.

In most electronics design plans, the design engineer doesn’t have a pre-determined knowledge of what the finished product’s power board requirements will be. This is because as the design process continues, the engineering team is presented with more feature additions and other revisions that will ultimately change the power requirements down the line. This is a costly and often risky way to execute a design plan, but it happens consistently: the power requirements are left as an ‘afterthought’ in the process. The result of this design method can be frustrating and expensive: a power solution that doesn’t match the requirements of the product or a lack of available space on the power board for additional power components to support these added features. When this happens, the entire power board must be re-designed. This translates into additional costs associated with re-design and materials, and slips in the market entry schedule – something a Best in Class manufacturer cannot risk.

Today’s class of advanced, drop-in POL modules offer a wide input design that can easily scale to support a range of power requirements from 2A to 20A, making it easy for design engineers to adjust power requirements on the fly throughout the design process. Further, DOSA-standard approved modules can help manufacturers reduce board space for power management solutions by as much as 50% - leaving room for all the components required to support today’s complex devices. And most important for design engineers, the drop-in POL component can accelerate the power design cycle by up to 70% - which can significantly reduce the entire design cycle.

Discrete POL: A Brief History

Discrete power solutions have traditionally provided a good power solution for board designers, and have offered some benefits and drawbacks. Benefits include good thermal impedance, lower electrical impedance, and the ability to optimize performance with capacitance. Traditional modules can tune capacitance to optimize performance, offering more flexibility to properly tune capacitance for a given application. However, this is often difficult and risky. If something is not designed correctly, it can cause catastrophic thermal events within the device. Other disadvantages of discrete solutions include board sprawl and power vias.

The late 1990s ushered in the adoption of the classic POL module, with a daughterboard and interconnect pins. It allowed components on both the top and bottom sides of the daughterboard, thus reducing the footprint significantly and freeing up space for more important parts. Yet the pins and the daughterboard were costly to source and design. Also, the pins increased electrical impedance and thermal impedance, degrading performance and resulting in higher electrical and thermal impedance.

In 2007, Land Grid Array (LGA) POL module solutions were introduced. This was a marriage of the best features of the discrete and classic module solutions. Since pins were the primary obstacle, the pins were removed but the daughterboard remained. The LGA POL module provided the best of both worlds. They removed power vias from the main board and also removed density by using a three dimensional inductor solution, rather than two sides of the daughter board. Removing the costly pins and moving to a single-sided board solution resulted in a much more inexpensive daughter board. It also reduced electrical and thermal impedances and improved the mating between the POL and main board. The LGA POL module was also a tunable solution. This meant that design engineers, for the first time, could realize the same benefits of the discrete solution because of the reduced capacitance. The tunable loop LGA POL module proved to be a much faster, easier, lower risk solution.

 Drop on in: The new modular design

The drop-in module is the next evolution of the LGA POL. The legacy, discrete POL design requires design, testing and layout costs, component data bases that must be created, CAD databases, design verification, and component testing and repair. A traditional, discrete POL design requires an experienced power supply designer for the lifetime of the project and a much longer lead time that allows the designer enough time to go through the complete design cycle.

With a drop-in module solution, pre-tested by the vendor/supplier, the 70% reduction in power supply design time means a faster time to market. Reduced costs associated with design and fewer parts, and consequently, fewer vendors to manage, is also a big bonus. And perhaps most importantly, drop-in modules take up less board space, which means there is now open area for more advanced feature sets. Drop-in modules offer a straightforward design process, minimal development costs and minimal pre-production training required from a design engineer.

In other words, when you are creating a discrete design, what you see is only the beginning. The visible part is the BOM that a discrete designer must put together. What lies beneath the surface are the design, testing, and layout costs, component data base that must be put together, CAD database, design verification, and the component testing and repair.

A discrete power design is cheaper than a POL module, but ONLY under the following conditions:

• An experienced Power Supply Designer must be available for the lifetime of the project
• There must be enough time to go through the complete design cycle
• Space is not an issue
• Design can be fully tested in the application
• Design is right the first time
• Volumes are high (200,000+ unit production volume)

Here are some of the advantages of a POL module solution:

• Faster time to market
• Reduced design costs
• Less board space
• Advanced quality testing to deliver billions of hours MTBF
• Known and characterized thermal behavior
• Proven quality
• Backwards compatible socket footprints
• Multiple standards-based supplier choices for supply chain efficiency

In regards to manufacturing issues:

• Discrete power solution
  • Discrete power components need to be assembled on application board
  • Have to integrate power components into process
  • Lower production yields due to power-related failure
  • Test of integrated power solution
  • Increased final expensive board scrap rates
  • Burn-in and/or HASS testing of power converter difficult
• POL power module solution
  • Straightforward process – automated placement on application board
  • Pre-tested and burned-in modules result in very low power-related initial failures
  • All SMT assembly of application board possible
  • Demonstrated field reliability data

In regards to operating performance and reliability:

• Discrete power solution
  • Difficult to optimize efficiency vs. function
  • Thermal options are limited
• POL power module solution
  • Usually higher electrical efficiency - due to more advanced circuit design
  • Robust thermal performance possible due to advanced packaging, PCB’s, potting, heat sinking etc.
  • High reliability due to extensive testing and qualification

In regards to solution costs:

• Discrete power solution
  • Development cost increases – varies depending on the complexity, can be prohibitive.
  • Startup component costs not optimized
  • Multiple discrete components must be sourced and managed by supply chain
• POL power module solution
  • Minimal development cost
  • Module component costs can be leveraged across multiple product designs to lower sourcing costs through increased volumes
  • Fewer components to be managed by supply chain

SIDEBAR: Five Questions to Ask Your POL Module Supplier If you are in the process of evaluating vendors who offer POL Modules, consider the following criteria:

• Are your modules DOSA approved?
• How long have you been in the POL industry?
• What is the extended output range of your modules?
• Do you offer design assistance consulting?
• What is the efficiency rating for your modules?