Real-life PCB design case study
The NLR was commissioned by the European Space Agency (ESA), to build a demonstrator for a new generation of on-board computers for satellites. The deadline was tight and the layout department of the NLR was too busy to handle this. Out of necessity the PCB design was outsourced to Sintecs.
Application Engineer Filip Fontaine and R&D Engineer Bert-Johan Vollmuller explain on behalf of the Dutch Aerospace Center why they outsourced this assignment while they could do it themselves and they tell about how they experienced the collaboration with Sintecs.
FFTC (Fast Fourier Transform Co-Processor)
NLR is developing a new generation of on-board computers for satellites. This contains a fast FFT-chip, which makes a whole new series of satellite instruments and data processing of satellite images possible. A demonstrator board around an FFTC chip developed by ESA must demonstrate all the possibilities of the chip and show that the FFT is indeed fast enough for the next generations of measuring instruments.
‘’For a demonstrator, it is enough that you perform the key components in space-qualified conditions,’’ explains Vollmuller. ‘’The FFTC itself, the FPGA for controlling the FFTC, and the three SDRAMs are implemented in rad-hard technology. The rest (power conditioning, the Space Wire interfaces for command & control and Space Fibre for date input and output) can be done in commercial components.
‘’Why outsource if you can do it yourself?’’
According to Vollmuller, NLR was under pressure of time because the board had to be ready by the end of 2018. “We developed the architecture and the scheme ourselves, and wrote the entire FPGA code. It is a complex board, with critical timing and very expensive components. A rad-hard FPGA costs ten thousand dollars. In principle, we can do the layout ourselves, but we did not have enough manpower in our layout department. We might not meet the deadline, resulting in a dissatisfied customer. Delay in planning is a much worse than the cost of the components. Therefore the complex layout had to be right in one go.”
“We liked the interaction between designer and layouter, in order to arrive at a good solution”
The NLR is used to do the layout in house. “This is a pleasant way of working, because there is a strong interaction between the engineer who makes the scheme and the layouter. We wondered how that would work if you outsource it and we were afraid that you give an order and see the first result 8 or 10 weeks later. Fortunately that was not the case,” says Vollmuller. Fontaine adds: “We had a lot of interaction during the layout phase, for example about the design decisions regarding the FPGA. In addition to the normal datasheet, there is a very thick book of application notes. Sintecs regularly contacted us to find out whether a design choice that we had made was intended. “Because something else is written in the application notes,” was the comment. In most cases we could say: ‘No, we really want it that way’, but a few times we thought ‘oh yes, that’s a good comment, we have to check that very carefully’. We would much rather have this than a layouter who does what we ask of him without thinking himself and that we would find out later that is not right yet. It is precisely this interaction between the designer and the layouter, in order to arrive at a good solution, that we liked. Sintecs actually did what we would normally do if we did the layout ourselves.
“The hardware functioned immediately without problems”
“Because there was a lot of interaction between us and the Sintecs layouter during the layout process, we had a lot of faith in the board. The result was that the hardware functioned immediately without any problems,” concluded Fontaine. “ESA was very enthusiastic that the project was completed before the end of 2018, and we at the NLR received compliments about that. Not only we are happy, our end customer is also happy. “