Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about how to select the FPGA chip. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

How to choose FPGA chips

In the process of FPGA design and development, I believe that many engineers should have encountered the headache of FPGA chip selection. Why is it a headache? To put it bluntly, it is not the disaster caused by the cost of research and development, ha, whether it is to the point. When doing design or R & D, large companies are better, and there are few problems that need to be selected by R & D engineers, except if you are in charge or in charge. In many small companies or small teams, the boss who doesn't know the technology will give you a word and you will take care of it. At this time, you should know what the words "you take care of" contain. The boss means that there is only so much money. For such a long time, you have to work harder. A little too straightforward, ha, then let's talk about how to select the FPGA chip, just for reference, exchange and learning, and common progress.

With regard to the selection of FPGA chips, this issue is really serious, because you have to consider both performance and cost, that is, the ratio of performance to price. Selection, we are sure to choose from the existing FPGA chips, this time will be a test of the engineer's breadth of knowledge reserve, if you know more and more detailed chips, that couldn't be better. If you have little contact, you need to read crazily at this time. The following is a brief talk about several manufacturers with more applications such as Intel, Xilinx,Lattice and Actel, and the selection of other manufacturers can be extended to similar choices.

First, prepare before type selection

When we do chip selection, at the beginning, we should make an estimate of the chip selection according to the actual situation of the project, and have an overall understanding of the chips that may meet the demand, that is to say, we should obtain as much information about the chip as possible. The easiest way to get information is through the official websites of these manufacturers, as far as Intel (Altera), Xilinx, Lattice and Microsemi (Actel) are concerned.

In general, the official website will list all the products according to the product series or applications, intuitively telling you the application of a series of products. For example, on Intel Altera's website, it will clearly mark its three major categories of FPGA products, high-end Stratix series, mid-range Arria series and low-cost Cyclone series. Some manufacturers publish a product selection manual every year, and many companies provide evaluation tools on their websites.

If you often visit the official websites of these manufacturers and read some overview documents, when you have a wide understanding of the product lines of various FPGA manufacturers, model selection will not be a big problem. Before determining the direction to be done, if you can find similar products, you can study the schemes used in these products. If you can't find them, you can search the database such as knowledge net, or take a look at the schemes adopted by others in similar directions. This is also a very good reference. It should be noted that many academic research programs are not validated by products, and some of them are lagging behind. In short, a comprehensive assessment is needed.

Second, the choice of FPGA manufacturers

As mentioned above, for Intel (Altera), Xilinx, Lattice and Microsemi (Actel), each manufacturer's products have their own characteristics and applicable areas. Choosing a manufacturer is relatively complex, and the following factors should be taken into account:

1. Special needs of the project. For example, if you want to choose the small size of the 4mmx4mm package and do not need to configure the chip FPGA, then maybe Actel is your only choice. If you need a FPGA chip with ADC, then maybe you can only choose some FPGA with ADC from Xilinx and Actel.

2. Look at the supply of chip manufacturers. A good supply channel will have a better guarantee for the mass production of the product, if there is no special channel or choose those models that are easier to buy and widely used.

3. Look at the quotation of the chip manufacturer. The lower price will reduce the cost of the product, especially when it is used in batches, save the cost, meet the functional requirements, and effectively improve the competitiveness of the product.

4. Look at our own technical personnel. It is the familiarity of the technicians to the products of all the manufacturers that meet the requirements. Using the most familiar products can effectively shorten the difficulty of development, reduce the development time, and improve the time to market.

5. Look at the maturity of the chip. Is there a better development software platform, whether there is better technical support, whether there are a large number of applications, whether resources can be easily obtained, and so on.

6.

Third, the selection of chip series

Each FPGA manufacturer has several series of products to meet the different requirements of performance and price in different applications. For example, for Intel Altera's FPGA products, it is mainly divided into three series, namely, high-end Stratix, middle-end Arria and low-end Cyclone. The specific performance features of each series of FPGA can also be found on the official website of Intel. In the selection, according to the actual project requirements, to select the appropriate series.

For example, if you need to achieve a relatively simple control function, the resource requirements are relatively low, and the cost control requirements are relatively high, then you need to start from the Cyclone series of FPGA to evaluate whether this series of FPGA can meet the requirements. However, if you want to do the validation of a relatively large ASIC chip, which requires high logic resources, bandwidth and running frequency of the FPGA, it is necessary to evaluate the FPGA of the Stratix series. There is a basic principle to pay attention to, the work that can be done with low-end chips, do not use high-end chips, the goal is to achieve the best balance between performance and cost.

Each series of FPGA chips may be divided into several generations of products, such as Intel Altera's Cyclone series, has now developed Cyclone,CycloneII,CycloneIII,CycloneIV and CycloneVI and other products. The upgrading of this product is largely due to the upgrading of semiconductor technology.

With the upgrading of semiconductor technology, FPGA chips provide more powerful functions, lower power consumption and better performance-to-price ratio in the process of upgrading. Then after determining a series of FPGA, which generation of products to choose becomes a problem again. Personal advice is that when there is no problem with price and supply, the newer the product, the better. You must not choose chips that have been or are about to be stopped by the manufacturer.

Any product has a life cycle, and the goal is to ensure that the life cycle of the chip used is not over in the product life cycle as far as possible. In the initial product planning to do chip selection, as far as possible to choose the manufacturer has just mass production or mass production of products soon, or even in the case of an exact supply channel, manufacturers can choose the chip to be mass-produced.

IV. Comprehensive consideration of the chip

For example, in the FPGA of the CycloneIII series, it is divided into two different subseries, the ordinary CycloneIII and the CycloneIII LS. In each subseries, it is divided into more models according to the resources in the chip. For example, the ordinary Cyclone III subseries contains eight types of chips, such as EP3C5,EP3C10,EP3C16,EP3C25,EP3C40,EP3C55,EP3C80 and EP3C120. Each type of chip distinguishes different chips according to the number of general I / O ports and packaging. For example, EP3C5 chips have four different chips: EP3C5E144,EP3C5M164,EP3C5F256 and EP3C5U256. And each kind of chip has different speed levels. For example, EP3C5E144 has four speed levels, C7, C8, and A7.

The following table lists the parameters of the FPGA of the ordinary CycloneIII series from different angles, which are derived from the official documentation of the CycloneIII chip:

4.1. The on-chip resource table of each type of chip. This table shows the on-chip resources for each type of chip, where Maximum User I/Os gives the maximum number of User iUniver O owned by that model, but it is important to note that the number of User iMager O owned by different packages is different.

4.2, the packaging information of each type of chip. The following table shows the package information for each type of chip, as well as the number of available Icano and the number of signal channels available for the chip under the package.

When choosing a specific chip model and package, a comprehensive consideration should be made according to the following aspects:

4.2.1, on-chip resources. Choose the appropriate on-chip resources according to the size of the design. This is a parameter that is difficult to determine. It is difficult to determine how big the design is and how many resources are needed on the chip. One of the recommended ways is to synthesize the previous design and map it to a chip to see how much on-chip resources need to be taken, and then evaluate the new design to be done with the previous size, and convert it to get the amount of resources needed on the chip. Another way is to complete the new design first, map it directly to different types of chips, and then evaluate which chip is appropriate. Another thing to pay attention to is that you cannot select a chip with just enough resources on the chip, leaving a certain margin for later design errors to be corrected and upgraded.

4.2.2, encapsulation. The choice of encapsulation mainly needs to be considered in two aspects, the first is the number of available Imax O ports. The second is the size of the package. The number of Icano is a necessary condition, and the available chips should be screened out according to this condition. Then, among the selected chips, the appropriate chip is selected according to the package type, size and pitch size. When the package size meets the requirements, try to choose the package that is beneficial to the design and production of PCB. For example, if there is a chip in TQFP package and the size meets the requirements of the project, then do not choose the chip in BGA package. For BGA encapsulated chips, if there is a pitch for 1.0mm can meet the requirements, do not choose pitch for 0.5mm. This directly affects the design difficulty, manufacturing cost and yield of PCB.

3. Speed grade. The speed level is a relatively independent parameter. It is necessary to compare the highest operating frequency that can be synthesized by the actual design with the required operating frequency, and choose the chip with slower speed as far as possible. When all the speed levels can not meet the needs, it is more necessary to improve the maximum operating frequency that the design itself can achieve from the perspective of optimal design.

The above is the editor for you to share how to choose the FPGA chip, if you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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