Originally designed to replace CD’s and DVD’s to distribute audio, SD and microSD cards are now commonly used in cameras, drones, mobile phones and tablets. SD and microSD cards continue to be the removable storage device of choice given their small size and capacity to retain huge amounts of data, on the footprint of a fingernail! With so many manufacturers in the market how do you differentiate them all and select the right card for your application? Most will be driven by price and capacity. But what about performance and quality? Should that be the driving factor when choosing SD and microSD cards? It really depends what you want to use it for.
Are you using the right SD card?
Industrial v Consumer
On the surface they look the same; identical mechanical design, same capacity and size. However, there are significant differences between industrial and consumer grade SD cards and flash devices in general. It is important to consider the impacts these differences have on reliability, endurance, compliance and total cost of ownership before selecting a device that is fit for your application.
Do your cards keep failing?
If yes, there is every chance you are using the wrong type of card. Using a consumer card in an industrial application may work for a while but will eventually fail. This can cause all kinds of headaches – machine downtime, fault finding, staff resource and angry customers. Something as humble and small as an SD card could help alleviate these issues if you spend a little more and seek expert advice to get the right card for your equipment.
It’s what’s inside that counts
Even when an SD card is opened (far left) to reveal its inner workings, it will look fundamentally the same whether a consumer or industrial card. However some manufacturers such as ATP offer SiP (System in Packaging, left) which completely encapsulates all contacts and components. Both cards will have a NAND Flash chip (the large block) and both will have a controller (the small block) . The NAND Flash is where everything is stored; data files, presentations, music, pictures and so on. The controller is the brains of the device – its the part that communicates with the host device and manages the flash file system directory. The controller is also responsible for wear levelling, error correction and garbage collection so is vital in making the cards work. Industrial grade cards can typically operate in temperatures of between -40°C to 85°C which is also known as wide temperature. Consumer cards typically can operate between -25°C to 85°C. So as you can see for applications that need to run in harsh environments for long periods of time industrial grade makes perfect sense.
Help is at hand
There are a plethora of card manufacturers and understanding which is right for your application can seem daunting. The technical team at Simms can help you by understanding your requirements; i.e. what the card is being used for, what data you are writing or perhaps it may be performance issues and the cards keep failing or data is being lost. The team at Simms are here to help. We are often contacted by companies that have purchased cards, (normally off the internet) as price is driving their choice and not the requirement.
Our experience has taught us if you understand the limitations of each technology and know the demands that are placed on card (specific to the application they are paired with) you can avoid costly failures and save on engineering resource.
With different types of NAND flash it is important that you chose the right one for your application. The table below, gives a brief outline of the characteristics for the different types of NAND Flash found in SD and microSD cards
|SLC||3D TLC||pSLC||Industrial MLC||TLC|
|P/E Cycles/ Endurance||*****||**||****||***||**|
|Warranty||5 years||2-5 years||2-5 years||2 years||2 years|
|Typical NAND Production cycle||5 years||1-2 years||3 years||3 years||6-12 months|
SLC or Single Level Cell is the highest grade of NAND Flash currently available and is used for industrial. By industrial we mean; aerospace, defence, transportation, energy, telecoms, infotainment, medical marine, offshore, manufacturing etc. applications. It is the best of the best. SLC is highly reliable but its expensive. SLC typically comes with a five year warranty . SLC products are typically bespoke manufactured.
3D TLC is a relatively new type of NAND Flash in which the memory cells are stacked vertically in multiple layers to achieve higher densities at a lower cost. 3D NAND is now becoming mainstream in consumer products with industrial applications becoming more readily available. Find out more about 3D NAND here
MLC or Multi Level Cell is one of the most common grades of NAND Flash. This is also used in industrial applications and is cheaper than SLC. However there is a trade off with speed, reliability and durability. MLC s suitable for products that may need a change of storage every 18-24 months and not heavily used. MLC can operate in wide temperatures and can be customised if its industrial grade.
TLC or Triple Level Cell is a version of MLC and is used for the consumer market. and the lowest grade of NAND flash. The endurance and cost is low and should not be used in any applications running operating systems or storing critical data. TLC is commonly found on the high street and on line, is widely available and cheap to manufacture. Demand for TLC will drop being replaced by 3D TLC
Bridging the gap with pSLC
Some companies have produced a NAND which bridges the gap between SLC and MLC, performance is generally better than MLC but not as good as SLC. Manufacturers such as ATP which use aMLC is a perfect example of this. The key differentiator with aMLC is the programme erase cycles (PE). The number of PE cycles is a number that a given device can sustain until problems occur. Each cycle causes a small amount of physical damage to the card and will accumulate over time then eventually fail. PE cycles for MLC range from 2-10K, aMLC 20k and SLC 60-100K depending on the manufacturer.
One of the underlying difference between Industrial versus consumer products is that Industrial grade is highly customisable. Vendors using clever technology and algorithms can manipulate the NAND Flash such as wear levelling which moves write cycles around the chip so that cells wear evenly; on-device duplication, which reduces the volumes of data written and so lowers wear; redundancy, which reserves a portion of the device’s capacity to replace cells as they fail; and write optimisation, which stores data writes so they can be made in large chunks to reduce the number of write operations. All clever stuff. But also the controller used in Industrial applications is far more effective than consumer grade. Companies such as Phison, Toshiba SMI and Hyperstone specialise in SD card controller technology.
Industrial grade cards are generally not high capacity. There is still a requirement for 128MB cards with the highest topping out at 128GB in MLC. As SLC is more expensive cards tend to stop at 32GB. Given SLC performance characteristics this capacity for most applications would be more than enough (remember the 60-100K programme erase cycles!). Consumer cards Using MLC and 3D TLC on the other hand are readily available in 256GB, 512GB and soon enough 1TB capacities.
|Features||Industrial Grade||Consumer Grade|
|Operating Temperature||-40°C to 85°C||-20°C to 85°C||Industrial grade has a far superior operating temperature|
|NAND Flash||SLC / MLC / 3D||3D / TLC||SLC is the highest grade, 3D TLC the lowest . MLC sits in between|
|Health monitoring||Yes||No||Real time monitoring that detects health status and provides product life expectancy|
|IOPS||Low||High||Performance measurement used to characterise storage. The higher the number the better.|
|Power protection||Yes||No||Data will be kept secure in a sudden loss of power|
|System in Package (see image below)||Yes||No||Protective covering leaving no components exposed to water, dust and humidity|
|ESD resistant||Yes||No||Electro Static Discharge resistant.|
|Advanced Wear levelling||Yes||No||An algorithm that evens the erase count to prolong product life expectancy|
|Autofresh||Yes||No||Reduces the risk of data loss|
|Dynamic Data refresh||Yes||No||Checks for errors, removes the bad data and prevents data corruption, extends the lifetime|
|Price||High||Low||Only the highest grade components are used in industrial cards|
|Controlled BOM||Yes||No||The build of materials can be controlled over the lifetime of a project to avoid incompatibility issues|
|Product registration||Yes||No||Unique part code for your product to ensure supply consistency|
|Lead times*||10-12 days||1-2 days||Industrial is bespoke manufactured to the end users requirements and may need customisation|