As microprocessors and ASICs have migrated toward lower supply voltages and higher currents, they have forced systems designers to adopt distributed power architectures. These architectures minimize the power distribution losses associated with centralized power schemes by placing dc-dc converters as close as possible to the chip for point-of-load conversion. That proximity enables them to maintain tight voltage regulation even in the face of high di/dt requirements, which would be adversely affected by the long pc-board traces required with a centralized supply.
Although power requirements dictate that the dc-dc converter must be placed as close as possible to the processor or ASIC being powered, pc-board space in many applications is at a premium. Therefore, systems designers need dc-dc converters to be as small as possible. In other words, they require converters with the greatest power or current density possible. As a result, power-conversion efficiency becomes a critical factor to the extent that every extra percentage point of efficiency becomes important.
In recent times, designers have had a number of options for implementing their point-of-load dc-dc converters. These range from fully discrete designs that might require as many as 100 components to generate a single high-current output, to fully integrated modular solutions. With the discrete approach, current densities are typically less than 5 A/in.2
International Rectifier Corp. (IR) now offers a higher-efficiency alternative to traditional discrete and modular solutions. iPOWIR, a unique modular power architecture for dc-dc converters, raises efficiencies and reduces design complexity by integrating the design- and layout-critical semiconductors into tightly packaged, power building blocks.
The blocks are multichip module (MCM) components. They will be offered, at least initially, in small BGA-style packages. Unlike other fully integrated converter solutions, they integrate only the critical silicon. To realize the complete converter design, some external passives are required off-chip. But the company claims that this approach yields unprecedented levels of efficiency. IR boasts a potential 2% improvement in overall end efficiency when measured against comparable, industry-leading dc-dc converter solutions.
Plus, there's the inherent design flexibility that the iPOWIR architect provides. First, it allows designers to select the external passive components as needed by the application. Furthermore, iPOWIR offers scalable solutions with initial products in this series each contributing 15 A of output.
Naturally, IR's iPOWIR-based solutions require less development effort than do discrete approaches. For example, using the iPOWIR architecture, the design of a 60-A dc-dc converter is reduced to less than 50 components with fewer than 10 devices per power stage. The resulting current density is 10 A/in.2—twice that of discrete alternatives.
According to the company, in general, iPOWIR can reduce overall converter size anywhere from 15% to 44% compared to existing discrete designs. When measured against modular alternatives, iPOWIR has achieved space savings as great as 58%.
Still, there's another advantage to iPOWIR that sets it apart from other approaches, both discrete and modular. As a leading supplier of power semiconductors, IR has the first crack at the cutting-edge MOSFET technology, and power MOSFETs play a critical role in determining power conversion efficiency. Essentially, that gives the company an ongoing potential to craft industry-leading dc-dc conversion solutions.
The first product in the iPOWIR series is the iP2001, a power building block for multiphase nonisolated synchronous buck converters (Fig. 1). The iP2001 integrates a high-speed MOSFET driver with high- and low-side MOSFETs, diodes, and passives in an 11- by 11- by 3-mm BGA package. It permits development of converters with an input-voltage range of 5 to 16 V and an output-voltage range of 0.95 to 3.3 V. The device operates over switching frequencies ranging from 300 kHz to greater than 1 MHz to deliver up to 15 A per phase, depending on the selection of the external multiphase controller and passives.
The company plans to follow the iP2001 with a fully integrated PWM controller for implementation of single-phase converters. Housed in a 14- by 14- by 3-mm BGA package, this building block will generate a 0.925- to 3.3-V output at up to 15 A (Fig. 2).