Articles Tagged ‘design’

Design considerations

Extra time and care should be taken when designing an embedded systems project. There are numerous factors to consider, and some of them might be a little bit more complicated than what you thought…

Lifetime

When we design a project, we would like to think that it will last forever. Of course, that is never the case, hardware becomes obsolete, minimum requirements change over time…

When designing a project, this is a factor that you need to take into consideration. If your project requires a specific component or microcontroller, has the manufacturer stated that he will continue to produce them for a certain amount of time? This component is cheat right now, but in a few years’ time, as it becomes increasingly difficult to source, that price is going to go up, eating into your margins. There might be replacement chips, but sometimes those devices have different footprints, requiring a rework of your PCB, or maybe a software change, requiring you to modify the source code. Most manufacturers will tell you when they plan to continue manufacturing parts (most will say 10 years), and if the site says “Not recommended for new designs”, it means exactly that!

Physical implementation

Some semiconductors and microcontrollers will exist in several packages. For example, the STMicroelectronics STM32F071CB exists in three packages: LQFP48, UFQFPN48 and WLCSP49. All three have the same amount of RAM, flash and clock speed, and are identical in almost every aspect. From a software point of view, there is know way of knowing the difference. However, the packages do have major differences.

The LQFP48 can be soldered by hand with a little bit of training (and the right hardware) but takes up 81mm2 on a printed circuit board (the package size itself is 49mm2).

The QFN variant is more complicated but takes up less space (the package size is still 49mm2, but significantly shorter leads mean that it only takes up a fraction more space on the printed circuit board). It also has the advantage of having a ground connector underneath, which helps with thermal dissipation. No routing directly under the chip!

The WLCSP49 variant is significantly smaller, taking up only 10mm2. For the same functionality, we go from 81mm2 of space on a PCB to 10mm2, but this comes at a price. Having pins in the centre of the package means that the printed circuit board will be more complex, and to check that all the solder points are correctly made, your board will probably have to be x-rayed.

Power Considerations

My first mobile telephone could run for over 10 days on the internal battery (and if needed, I could even replace the rechargeable battery with 4 AA batteries, you can imagine the size). No-one wants to recharge their telephone several times a day, there has to be a balance between energy consumption and energy efficiency. There are different technologies, from high clock speed and deep sleep, to low clock speed low power consumption devices. Which one is right for you?

Price

At the end of the day, what matters is that your product brings you in some money. Engineers, sales staff, IT workers, everyone depends on your product. Your future research and development depends on the product that you sell, without cash income, there is no spending, and no new product. Does your product really require an application processor, or is a micro-controller sufficient? It's the difference between several dollars and tens of cents. It's the difference between a product that can sustain your company, and one that will be a red line in your accounts.

Our advice

We will always give you at least 3 choices, each with their advantages and disadvantages, to help you decide which product is right for you.

So how can we help you? Contact us