10-03-2014 01:56 PM
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 )
10-03-2014 11:43 PM
MLC Flash devices cost less and allow for higher storage density.
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.
10-04-2014 01:41 AM
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.
10-04-2014 10:50 AM
[ That's why I want to know which card uses 2 bits per cell. ]
The multi-level cell (MLC) is a memory element capable of storing more than a single bit of information.
10-07-2014 07:50 PM - edited 10-07-2014 07:53 PM
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?
10-07-2014 09:55 PM
1- [ SDSDQM-008G-B35 (8GB microSDHC card). We would like to know if this is SLC/MLC/TLC type? ]
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.
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 caused by a large gate voltage, Vg, is used to bump electrons up from the channel onto the floating gate.
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/
10-07-2014 10:45 PM
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?
10-07-2014 11:27 PM
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.
Regards, Alfred. (Google translated)
10-09-2014 01:13 AM - edited 10-09-2014 01:13 AM
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
So probably we do not have much choice but to continue using this card.