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FPGA是在各种应用程序中的数字设计工程师中的流行选择。它们是微控制器设计的替代方法，它需要专用功能高速。在某些情况下，FPGA消除了创建昂贵的自定义ASIC的需求。它们的低成本和尺寸范围使它们在工业，医疗，航空航天，防御甚至一些消费产品中都有用。
But while engineers are happy with their FPGA design solutions, many quickly discover that it causes another problem. Some are surprised to find that each FPGA requires multiple, critical dc voltage supplies. Four to six or more dc rails are needed in many instances, creating a need for a special power supply solution. That’s usually a big problem, but there are ready-made answers to this knotty problem.
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功率难题
当今，大多数产品使用的标准电源轨电压为12、5和/或3.3 V.另一方面，如果采用了FPGA，则功率供应电压需求大大不同。需要在高电流水平下低至0.72、0.85和/或1.0 V。其他常见的FPGA导轨需求包括1.5和1.8 V，目前的水平也相对较高。较低的电压通常为设备的核心供电，而其他电压则为内存，收发器，IO电路和辅助电路。
This problem shows up when special high-speed processors are being designed in, too. Again, multiple low-voltage/high-current rails are needed.
Besides the requirement for multiple rails, each has its own specifications for current, voltage accuracy, ripple, load transients, and sequencing. The数字shows common solution. One of the main power sources is stepped down with a dc-dc converter to form an intermediate rail. Then the individual power rails are created with a point-of-load (POL) regulators, switchers, or LDOs as seen fit. And a sequencer is essential.
FPGAs are typically powered by individual POL regulators driven from a common power rail.
With regard to voltage accuracy, the FPGA core and transceivers usually require 3% or better. Accuracy for IO and auxiliary supplies are typically less than 5%. Voltage tolerance range should be less, too—that range is made up of ripple around the set-point voltage plus the regulation percentage. Ripple levels are specified for the device used. Then there’s the tricky sequencing problem. The supplies positively must be turned on and off in a prescribed sequence. The usual requirement is core supply comes first, transceivers at the same time, and then auxiliary circuits followed by IO circuits.
There are multiple ways to sequence the supplies. You can use RC network delays, having one supply enable the next supply, or by controlling the whole thing with an available microcontroller using its timers and GPIOs. However, the best solution is to use an IC specially designed for the job.
简单的出路
如果您是数字设计师，正在寻找快速而简单的解决方案to the multi-rail power problem, you can seek out ready-made products that directly address your power needs. Texas Instruments is one vendor of power products with multiple solutions.
The quickest choice is to use a power module. An example is TI’s LMZ30602 power module that combines a 2-A dc-dc converter with power MOSFETs, a shielded inductor, and passives into a low-profile, 9- × 11- × 2.8-mm QFN package. This IC requires only three external components and eliminates the loop compensation and magnetics part of the design process. Just add capacitors and voilà. Other modules in this series have a wide range of input-rail voltages, output voltages, and current ratings.
另一个解决方案是寻找可用的参考设计。ti提供了其中几个，例如TIDA-01366（也称为PMP9799），这是Altera流行最大10 FPGA的完整电源解决方案。这种简单的解决方案仅使用三个DC-DC转换器，可以有效地为最大10（89％至92％）和成本效益。TI设计支持众多工业应用，并需要任何需要较小，高效率高的电源的应用。另一种TI参考设计解决了Xilinx的Ultrascale/Ultrascale + FPGA产品的需求。
Also don’t overlook available vendor design tools. One of these is TI’s WEBENCH FPGA Power Architect. It will take your requirements and walk you through to a solution with specific parts recommendations.
如果你设计r own supply with dc-dc converters, take a look at the Texas Instruments’ LM3880 simple sequencer to solve the turn-on timing problem.
For you digital designers, continue to enjoy the benefits of your FPGA and the comfort that comes from knowing that电力供应解决方案are readily available.
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