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Now that the different design approaches to achieving a power supply in a system design are understood, it is possible to view a simple cost example requiring a power management solution. The example consists of a networking board utilizing an FPGA as the core processor. The following power rails are required on the board: one 6A rail for the FPGA, one 5A rail for the FPGA memory, one 5A rail for the bias rails, one 4A rail for the microprocessor + support circuits, one 2A rail for the general purpose controller, and one 3A rail for the general purpose input and output ports. There are six power rails in a system totaling 25A. When deciding on whether to design a power subsystem with either discrete components or a module, there are important considerations that must be thought through carefully before beginning the design. The first is design experience. Does the engineer have the necessary design expertise to build a stable power supply using discrete components? Project design engineers today focus on digital technology and may not have the necessary power expertise to design a reliable discrete power supply. The second consideration is the man hour cost. If the engineer does not possess power design experience, the man hour cost in design and development time may not be economical. In this case, other design alternatives, such as a module approach, should be considered. Time to market is typically a key goal. Many manufactures have opted to use power modules because of the simplicity of the power design, which also saves space on the PCB board layout. Many infrastructure designs today consist of twenty to thirty individual power rails on a single board. Using a power module will meet most high power density design specifications in a very small PCB board area.

PTM Published on: 2015-10-16