The history of eMMC and its advantages VS disadvantages

If we want to know the development of eMMC, we need to introduce the history of flash firstly.

Pls check below for more information about the characteristics of various storage structures.

Screen shot from Overview of NAND and NOR Flash Memory Products

The development of NAND Flash storage is from SLC, MLC to TLC, QLC, which is beyond Moore's Law.

At the beginning, the NAND Flash mainly adopt SLC (Single Layer Cell). At the year of 2003, MLC (Multi Layer Cell) was adopted as the storage units till now. And then the mainstream storage units have moved from MLC to TLC (Triple Layer Cell) and even QLC. Since 2017, the mainstream production process also changed from 2D to 3D. With the development of nano processing technology, the capacity of NAND Flash increase rapidly. while the cost of per unit storage capacity reduced significantly.

However, its disadvantages appear easily. From the original 1bit/cell to the later 4bit/cell, the calculation is more complex, the error rate is inevitably higher, and erasable life is shorter. In this case, the MLC and TLC Flash need to be equipped with a high-performance controller to provide flash management such as EDC, ECC, and average rewriting.

SLC=Single Level Cell, 1bit/cell. fast R/W speed, long life, the price is more than three times than the price of MLC, and P/E-Cycle can reach 100,000 times.

MLC=Multi Level Cell, 2bit/cell, with average speed, average life, average price, and about 3000-10000  life times.

TLC=Triple Level Cell, 3bit/cell. It is slow, short in life, cheap, and about 500 times R/W. The technology is gradually growing.

QLC=Quad Level Cell, namely 4bit/cell, promoted in 2019, meet the mainly requirements of the larger capacity and lower cost. Performance, speed and erasable life are all lower than TLC.

Moore's Law was proposed by Gordon Moore, one of the founders of Intel. When the price remains the same, the number of transistors in the integrated circuit will be doubled every 18 months, and the performance will also be increased doubled. In the other words, the computer performance for every dollar will more than double every 18 months. But for the NAND Flash industry, the cycle of Moore's Law is only 12 months.

The application field of eMMC

The embedded eMMC came into being with the worldwide popular for the tablet and smartphones in recent years. The rapid development of smart phone and tablet computer triggered the upgrading of electronic products. The various applications such as multimedia player, HD camera, GPS put forward higher requirements for storage hardware, high capacity, high stability and high R/W speed, but small size. However, with the development of nano fabrication and storage technology, the performance of NAND Flash is declining; P/E-Cycle is short, the error probability is high; the R/W speed is slow; and the stability is poor. It can’t meet the requirement of the smart electronic devices. Then, eMMC come out and just can fill the gap of market demand.

eMMC (Embedded Multi Media Card) adopt a unified MMC interface. eMMC is a product which assemble the high-density NAND Flash and MMC Controller in a BGA chip. eMMC have a controller which can manage the Flash, including EDC/ECC, rewriting, bad block management, power failure protection and other technologies. Users do not need to worry about changes in manufacturing process of the flash wafer. At the same time, a single eMMC chip saves more PCB space.

The development direction of eMMC

Interface: The eMMC interface will gradually switch to the UFS interface, which is faster. Now, the mainstream mobile phones and tablet products have adopted the UFS interface.

Internal structure: The flash of eMMC has switched to 3D TLC wafers. But there are still a few eMMCs using MLC on the market. This kind of eMMC is mainly for the industry market.

Capacity: For eMMC interface, the biggest capacity for eMMC is 128GB, and bigger capacity of eMMC products, the interface will change to UFS interface.

Size:  the size is 12*18 for former eMMC, now the mainstream is 11.5*13mm, and we also can choose 7.5*9mm. Pls check this link for more information: http://www.longsto.com/product/34.html

CS SD NAND, we can called it mini-eMMC, the size only have 6*8mm, 8 pins.

Pls check this link for more information:

https://www.longsto.com/product/68-en.html

The advantage and disadvantages of eMMC

Advantages:

1. Big capacity

2. Fast R/W speed

3. Good compatibility

4. Wide selection for flash. The firmware can deal with any kind of flash.

Disadvantage:

1. High cost. Usually the smallest capacity of eMMC is 16GB, if customer only need 128MB, he also need to pay the money for 16GB.

2. Big size. The size of 11.5*13mm is too big to design IOT Devices.

3. The layer of PCB is at least 4. The eMMC adopt pin-BGA153 package technology. The distance for each pin just have 0.5mm. When the PCB is too small, it is easy to make errors.

4.The MCU compatibility is limited. Many IOT platform can’t support eMMC(But can support SDIO)

5. P/E-Cycle is only have 500 times.

The storage solution for IOT devices:

CS SD NAND is a kind of mini eMMC which can solve all below eMMC’s disadvantages.

Below link FYI.

Comparation between SD NAND and eMMC: https://www.longsto.com/news/328-en.html

CS SD NAND more detail information: https://www.longsto.com/product/68-en.html

If you have any questions, please contact us

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