DSP or FPGA? How to choose the right device

By Bamdad Afra and Amit Kapadiya, Nuvation
May 07, 2008 -- dspdesignline.com

DSPs and FPGAs both offer advantages for signal processing. Here are the design guidelines you need to choose between DSPs, FPGAs, or a combination of the two. Topics covered include device cost, performance, NRE, and availability of application-specific features.

System designers face a number of key questions during the architecture phase of their project. Increasingly one of these questions is whether to use an FPGA (field programmable gate array) or a DSP (digital signal processor). To answer this question, system designers consider parameters such as:

System performance requirements for signal processing
Power consumption
Component count and form factor
Future product/system road-map and upgradeability for the system
Economic parameters such as non-recurring engineering (NRE) investment, bill-of-materials (BOM) cost, time-to-market and project risk

The decision also depends on the technology familiarity factor. In some cases, the design team is well-versed in DSP systems but has little FPGA background, or vice-versa. In such cases, the team skill-set may drive the choice between FPGA and DSP. For example, Nuvation recently worked on an algorithm acceleration project where the algorithm lent itself to wide parallel implementation in an FPGA. However, classic FPGA approaches were ruled out due to the lack of FPGA skills in the client's engineering team and the potential barriers this presented to product lifecycle maintenance.

We acknowledge that most engineers and system architects are more familiar with DSP technology due to the simplicity of designing with DSPs. This is a clear advantage for DSPs. However, developer familiarity varies widely across design teams, so it is difficult say how important this issue is to a "generic" design team. Thus, this article ignores this DSP advantage and assumes that the choice of technology does not depend on developer familiarity.

In order to choose between FPGA and DSP, we look at system performance requirements for signal processing and BOM cost. We consider devices from a major DSP vendor (Texas Instruments) and a major FPGA vendor (Altera) to guide us through this process. We identify some of the signal processing applications in which each specific technology is clearly superior. We also consider where an FPGA may be used as a co-processor to a DSP chip.

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