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Flash memory selection – Our checklist for design engineers

A design engineer has to come up with a product that’s achievable in the real world from a cost and a components point of view. That means ensuring some very important points are considered. 

Flash memory has a role to play in most of the technology we use day to day, including in industrial sectors. So design engineers that work in tech need to have a good understanding of the capabilities of different types of flash, form factors and specifications in order to decide what is the best fit for whatever it is they are working on.  

I’ve blogged already about the pros and cons of embedded or removable flash memory, and deciding which to use is just one of the many questions a design engineer needs to answer when specifying flash for their next project. Here’s a checklist of some of the other important questions that need an answer. 

What are the most important performance parameters that cannot be compromised? 

The initial specification for a product will outline what the device does, and its Unique Selling Point. It will be vitally important to make sure that the flash memory selected allows the product to do what it sets out to do. If cost savings need to be found, there will be lines in the sand that can’t be crossed. One of these should be the minimum specification for flash memory. 

Does the product meet speed requirements? 

Different flash memory functions at different speeds. The very latest SD Association specification, called SD8.0, caters for 8K video capture. That’s at the leading edge of speed, but it is only required by a small subset of devices. It is important to ensure that the speed requirement is met, including being sure that a card specified at the outset can meet any required future uplift in speed requirements.  

Will the product operate at extreme temperatures? 

While design engineers involved with consumer products don’t have to worry too much about temperature thresholds, there are plenty of situations where temperature tolerance is crucial. Mining, manufacturing and military scenarios can all require memory cards that can withstand extremes of heat or cold. Even automotive applications have to handle temperatures ranging from below freezing to summer heat in the Middle East, and the memory has to work instantly when the engine is switched on. Specify less tolerant flash memory and the entire product will be compromised. Our experience working with a leading automotive manufacturer illustrates the importance of selecting the right flash memory. 

Will the product operate at the required humidity level? 

As with temperature, so with humidity. If a product will be used in situations where there is a lot of water vapour in the air then the cards need to be certified to withstand this. Standard, consumer grade cards just won’t fit the bill. There are many situations where this can apply, such as in products for use in countries with humid weather conditions, or those made for smart home, work or leisure locations with a humid atmosphere.   

Does the product meet requirements for lifespan? 

Every time data is written to or deleted from flash memory there is a little bit of wear and tear. Different techniques are used to help minimise wear. Typically, consumer grade cards, which are the least expensive, have the least protection, and so will have the shortest lifespan. If a design engineer is working on a product that might have a short life, or few read/write demands, then consumer grade cards might be fine. But a broken card, especially if it is embedded memory, can mean a broken product, so it’s important to get the cost/longevity balance right.  

Will the product perform in dusty environments and withstand vibration? 

In addition to extremes of heat, cold and humidity, flash memory can be required to function reliably in a number of other challenging conditions. It might be used in environments where there are a lot of dust particles, or where there is continuous vibration, for example. These situations are more common than we might think. Cards with this capability are required by police, fire and rescue services, and in many different types of diagnostic equipment.  

Do I need the flash to be customised or optimised to work with my product? 

Sometimes a device maker wants to customise the way users interact with a flash memory card. This is entirely possible, and if it is required then the design engineer will need to specify that they need embedded flash memory with this capability supported.  

Is the product consistent and repeatable?  

A design engineer will need to feel confident that the specification they settle on is one that can be achieved by the supply chain in a reliable and consistent way over time. A flash memory card is made from a range of components, and if product build and manufacture is to be consistent, manufacturing costs kept constant, and a steady supply of product in the required quantities guaranteed, then consistent supply of flash memory also needs to be guaranteed. Ensuring this is known as having a fixed Bill Of Materials. 

What level of technical and engineering support is available to me? 

It is vital that a design engineer specifies a product that can actually be built within the required timeframe and to the required cost. They will need to be sure that any additional design and manufacturing support, such as engineering, technical, and plant, is available to the required level.   

  

Author: Paul Norbury

Date: Friday 31st July 2020