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Newbie
Posts: 2
Registered: ‎10-03-2014

Which are MLC / TLC MicroSD cards?

 

I like to buy the MLC MicroSD card that uses MLC technic, that will lessen the chance / time that data corrupts.

Both types corrupt after certain cycles of erase/programming, but MLC will last longer.

 

So my question is: Which Sandisk MicroSd cards are based on MLC?

(why is this information not published as public data? Professionals or serious users  like to know )

 

Thanks!

SanDisk Professor
Posts: 478
Registered: ‎11-27-2013

Re: Which are MLC / TLC MicroSD cards?

Smiley Happy   Hi Chihwahli,


Dear member of SanDisk Community, welcome.


For more certainty, also you can send the question to the Support Team: Link: http://kb.sandisk.com/app/ask/


Friend:


Single-level cell (SLC) and multi-level cell (MLC) Flash memory are similar in their design.

MLC Flash devices cost less and allow for higher storage density.
SLC Flash devices provide faster write performance and greater reliability, even at temperatures above the operating range of MLC Flash devices.


These factors make SLC Flash a good fit in embedded systems, while MLC flash makes it possible to create affordable mobile devices with large amounts of data storage.


In order to select the right Flash memory for an application, it is important to analyze the how it will be used.


For example, product developers integrating memory into a portable barcode reader will most likely need SLC Flash since performance and durability are important.
On the other hand, a company building a portable media player will need the low cost and high density of MLC to price their device competitively.


SLC Flash is used in commercial and industrial applications that require high performance and long-term reliability.
Some applications include industrial grade Compact Flash cards or Solid State Drives (SSDs).


MLC Flash is used in consumer applications that do not require long term reliability such as consumer grade USB Flash drives, portable media players, and Compact Flash cards.


The read speeds between SLC and MLC are comparable. Reading the level of the Flash cell compares the threshold voltage using a voltage comparator. Thus, the architecture change does not affect sensing.
In general, the read speeds of Flash are determined by which controller is used.


The endurance of SLC Flash is 10x more than MLC Flash.
The endurance of MLC Flash decreases due to enhanced degradation of the substrate.
This is a main reason why SLC Flash is considered industrial grade Flash and MLC Flash is considered consumer grade Flash.

 

Higher temperatures cause more leakage in the cells. Combined with the increased sensitivity required to differentiate between the levels, this leakage will cause the sensors to read the wrong level.
As a result, the operating temperature of MLC spans only the commercial range.
Leakage is not significant in SLC Flash and thus, it can operate in an industrial temperature range.


Then, it is important to evaluate what type of Flash memory your system needs.


If performance and durability are essential for your system, SLC Flash incorporated.
If low cost and high density are essential, MLC Flash is the right choice.


The high-performance MLC technology with three bits per cell, is commonly referred to as Triple Level Cell (TLC), which uses eight states.


Enjoy!!


Regards, Alfred.

Newbie
Posts: 2
Registered: ‎10-03-2014

Re: Which are MLC / TLC MicroSD cards?

Thanks for this initial answer.

 

I have frequent erase and proram cycles with my micro SD card. That's why I want to know which card uses 2 bits per cell.

The SLC cards are just too expensive, those are out of my reach.

 

Will ask the support team and put the answer here if I get it.

SanDisk Professor
Posts: 478
Registered: ‎11-27-2013

Re: Which are MLC / TLC MicroSD cards?

Smiley Happy   Hi Chihwahli,

 

[ That's why I want to know which card uses 2 bits per cell. ]

 

Well,

 

The multi-level cell (MLC) is a memory element capable of storing more than a single bit of information.


MLC NAND flash is a flash memory technology using multiple levels per cell to allow more bits to be stored using the same number of transistors.


MLC NAND flash memory has four possible states per cell, so it can store two bits of information per cell.


MLC Flash is used in consumer applications that do not require long term reliability such as consumer grade USB Flash drives, portable media players, and Compact Flash cards.

 

Luck.

 

Regards, Alfred.

KSP
Newbie
Posts: 4
Registered: ‎10-07-2014

Re: Which are MLC / TLC MicroSD cards?

[ Edited ]

Hi Cacho

 

I also have a clarification regarding the Cell type for the microSDHC we are presently using in our product.

 

The card  currently used is SDSDQM-008G-B35 (8GB microSDHC card). We would like to know if this is SLC/MLC/TLC type?

 

The intended use of this card is to save both program and user data for our product which we are designing. Since this serves as storage space for all codes-  including system and application code, high reliabilty is preferred since any failure on the card can render the product unusable. 

 

Does the above card fall under the more reliable SLC category?

 

 

Thanks!

 

Regards,

KSP

SanDisk Professor
Posts: 478
Registered: ‎11-27-2013

Re: Which are MLC / TLC MicroSD cards?

Smiley Happy   Hi KSP,


Dear member of SanDisk Community, welcome.

 

1-  [  SDSDQM-008G-B35 (8GB microSDHC card). We would like to know if this is SLC/MLC/TLC type?  ]

 

Is MLC.


2-  [  Does the above card fall under the more reliable SLC category?  ]


2.1-   SLC Flash is used in commercial and industrial applications that require high performance and long-term reliability.
Some applications include industrial grade Compact Flash cards or Solid State Drives (SSDs).

 

2.2-   Traditionally, each cell has two possible states, so one bit of data was stored in each cell in so-called single-level cells, or SLC flash memory.

SLC memory has the advantage of faster write speeds, lower power consumption and higher cell endurance.

 

However, because SLC memory stores less data per cell than MLC memory, it costs more per megabyte of storage to manufacture.

 

Due to faster transfer speeds and longer life, SLC flash technology is used in high-performance memory cards.

 

2.3-   It is important to understand what makes up a Flash cell, before explaining the variation between SLC and MLC Flash.


Each cell consists of a single transistor, with an additional “floating” gate that can store electrons.

A large voltage difference between the drain and the source, Vd – Vs, creates a large electric field between the drain and the source.


The electric field converts the previously nonconductive poly-Si material to a conductive channel, which allows electrons to flow between the source to the drain.

 

The electric field caused by a large gate voltage, Vg, is used to bump electrons up from the channel onto the floating gate.
As an electron travels closer to the drain, it gains more momentum and thus, more energy.

 

But, this amount of energy is not enough to push an electron onto the floating gate.

Electrons with high momentum near the drain can sometimes bump into Si (Silicon) atoms .

This bump gives the electron enough energy to be pushed onto the floating gate.

The number of electrons on the floating gate affects the threshold voltage of the cell Vt.

This effect is measured to determine the state of the cell.

 

2.4-   SLC Flash stores one bit value per cell, which basically is a voltage level. The bit value is interpreted as a “0” or a “1”.

Since there are only two states, it represents only one bit value, each bit can have a value of “programmed” or “erased.”

 

 

For more data, you can send the question to the Support Team: Link: http://kb.sandisk.com/app/ask/


Enjoy!!


Regards, Alfred.                                                                                       (Google translated)

 

 

 

 

 

 

 

KSP
Newbie
Posts: 4
Registered: ‎10-07-2014

Re: Which are MLC / TLC MicroSD cards?

Hi Alfred

 

Thanks for the very detailed description and also insights on the cell structure. Very informative and detailed.

 

Does it mean that SLC technology is not used for microSDHC card types since it is not cost efficient? 

 

Regards,

KSP

SanDisk Professor
Posts: 478
Registered: ‎11-27-2013

Re: Which are MLC / TLC MicroSD cards?

Smiley Happy   Hi KSP,

 

However, SLC technology is used for microSDHC card types.

 

It depends on the manufacturer, if you consult different brands, see what some utlizan this topic, as a marketing tool.

 

Other companies, do not say anything about this, because they are trade secrets.


In case of SanDisk, please, consult to the Support Team, link: http://kb.sandisk.com/app/ask/

Luck, and then you tell us, what happened, please.

 

Regards, Alfred.                                                            (Google translated)

KSP
Newbie
Posts: 4
Registered: ‎10-07-2014

Re: Which are MLC / TLC MicroSD cards?

Hi Alfred,

 

Thanks, again.

I have posted the query with the support team. Shall updateh ere once i get response from them Smiley Happy Smiley Happy

 

Regards,

KSP

KSP
Newbie
Posts: 4
Registered: ‎10-07-2014

Re: Which are MLC / TLC MicroSD cards?

[ Edited ]

Hi Alfred

 

I am afraid I do not have anything else to add to this conversation. The customer service  replied back saying they do not disclose such details regarding cell structures Smiley Sad

 

So probably we do not have much choice but to continue using this card.

 

Regards,

KSP