SanDisk iNAND Flash and microSD

New heights in mobile storage: SanDisk iNAND and microSD full range

In today's era of constantly iterating smart devices, consumers' demands for storage capacity, response speed, and data reliability continue to rise. From flagship smartphones to industrial embedded systems, from 4K ultra high definition video recording to all-weather surveillance cameras, flash storage has become one of the core components that determine user experience. SanDisk (now Western Digital), relying on decades of innovation in the flash memory industry, has launched a complete line of iNAND embedded flash drives (EFDs) and OEM microSD cards, covering consumer electronics, industrial control, edge computing and other scenarios. This article will provide a comprehensive technical analysis of the iNAND family and OEM microSD cards from the dimensions of product architecture, core technology, model specifications, application adaptation, and ecological cooperation.

SanDisk's technological accumulation and vertical integration advantages

As a leading global provider of flash memory solutions, SanDisk has deep partnerships with all mainstream smartphone and tablet manufacturers, possesses a complete market segmentation product portfolio, and has established partnerships with all major chipset suppliers. Through its joint venture wafer fab with Toshiba (now known as Kaixia), SanDisk has gained world-class NAND flash memory manufacturing capabilities. Its vertically integrated business model significantly shortens the cycle from research and development to mass production, enabling rapid delivery of innovative, reliable, and high-performance storage solutions, providing OEM customers with flash optimized hardware and software that combines high density and low cost.

In addition, SanDisk actively participates in standard organizations such as JEDEC and SD Association, playing a key role in promoting the development of industry standards for the future of mobile computing. The deep collaboration of this ecosystem enables the iNAND series to seamlessly integrate with the latest operating systems, application processors, and mobile networks.

INAND Embedded Flash Drive (EFD) Product Line

The iNAND series adopts the industry standard e.MMC interface (embedded multimedia card), supports HS400 high-speed mode, and can be quickly integrated into new devices. They not only provide storage space for high-capacity music, photos, videos, and virtual reality content, but also significantly enhance the user experience of multitasking, fast switching between applications, and high-speed continuous shooting of high-resolution images.

The iNAND series currently includes three models: iNAND 7350, iNAND 7232, and iNAND 7250, which are designed to meet different performance requirements and cost targets.

1. iNAND 7350: High Performance 3D NAND Flagship

The iNAND 7350 is a high-performance e.MMC drive using 3D NAND flash technology, designed specifically for today's demanding mobile applications. 3D NAND achieves higher capacity while improving read and write performance and reliability within the same physical area by vertically stacking storage units. This model has a capacity ranging from 32GB to 256GB and is packaged in a small size (11.5mm × 13mm) with a thickness of 0.8mm to 1.2mm depending on the capacity. The interface standard is e.MMC 5.1 HS400, which provides excellent sequential read and write speed and can significantly reduce file transfer time, system startup time, and application startup time. Suitable for flagship smartphones, tablets, and AR/VR devices that require high-density storage.

2. iNAND 7232: SmartSLC technology accelerates 4K video recording

The biggest highlight of iNAND 7232 is its second-generation SmartSLC technology. This technology operates a portion of TLC or MLC flash memory in SLC mode, dynamically allocating SLC buffers when high-speed writing is required, significantly improving sequential write performance. This enables iNAND 7232 to smoothly record 4K and Ultra High Definition (UHD) videos, avoiding frame drops or recording interruptions. The capacity range is 16GB to 128GB, and it also uses the e.MMC 5.1 HS400 interface. The package size is similar to the 7350 series, and the thickness is slightly higher (1.2mm for 128GB). This model is very suitable for mid to high end smartphones, sports cameras, and any device that requires high bitrate video recording.

3. iNAND 7250: Industrial grade wide temperature reliability

INAND 7250 is a commercial grade e.MMC flash drive, particularly suitable for industrial applications. It provides high reliability and durability across a wide range of working environments. The capacity ranges from 8GB to 64GB, and the interface is e.MMC 5.0 HS400 (written as 5.5 in the document, suspected as 5.0, according to the original e.MMC 5.5 HS400, but 5.1 is commonly used in the actual standard, and the original text is retained here). The package size is 11.5mm × 13mm, and the thickness ranges from 0.8mm to 1.2mm. The iNAND 7250 is capable of stable operation within a wide temperature range of -25 ° C to 85 ° C (and even up to 95 ° C for some specifications), adapting to harsh environments such as industrial automation, outdoor equipment, and in car infotainment systems.

Comparison of iNAND series technical specifications

The following table summarizes the key parameters of three iNAND products (based on the original document):

Model iNAND 7350 iNAND 7232 iNAND 7250

Capacity 32GB -256GB 16GB -128GB 8GB -64GB

Interface e.MMC 5.1 HS400 e.MMC 5.1 HS400 e.MMC 5.5 HS400

Package (mm) 8GB: 11.5 × 13 × 0.8

16GB: 11.5×13×0.9

32/64GB: 11.5×13×0.8/1.0

128GB: 11.5×13×1.0

256GB: 11.5×13×1.2 16GB: 11.5×13×0.9

32GB: 11.5×13×0.9

64GB: 11.5×13×1.0

128GB: 11.5×13×1.2 8GB: 11.5×13×0.8

16GB: 11.5×13×0.9

32GB: 11.5×13×1.0

64GB: 11.5×13×1.2

Technical highlights include 3D NAND, high-performance second-generation SmartSLC, 4K/UHD video optimization, industrial grade wide temperature range, and high reliability

OEM microSD card series: reliable edge storage and application performance

In addition to embedded flash memory, SanDisk also provides OEM customers with a rich line of microSD card products to meet the needs of storage expansion, edge device data recording, and mobile application performance improvement.

1. SanDisk Edge microSD card: 3D NAND driven edge storage

SanDisk Edge microSD card is a commercial grade storage card that uses 3D NAND technology to provide reliable and secure edge storage. It meets stringent safety, capacity, performance, and environmental requirements. The capacity range is from 16GB to 256GB, which can store up to 60 hours of full HD video (based on 256GB). This card is suitable for surveillance cameras, dashcams, drones, and other commercial applications. Its speed level is U3/V30 (video speed level 30), ensuring a continuous write speed of not less than 30MB/s, meeting the requirements of high-resolution video recording. The working temperature range is -25 ° C to 85 ° C, suitable for outdoor and vehicular environments.

2. SanDisk OEM A1 microSD Card: Breakthrough in Application Performance Level 1

The SanDisk OEM A1 microSD card is one of the first products in the industry to meet the application performance level 1 (A1) requirements of the SD Association 5.1 specification. The A1 standard defines the minimum requirements for random read and write performance: 1500 random read IOPS and 500 random write IOPS, while ensuring at least 10MB/s sequential performance. The card has a capacity of up to 256GB, allowing consumers to use microSD cards as internal storage for additional capacity, faster speeds, and a better smartphone experience. This is particularly important for entry-level and mid-range phones that do not support high built-in storage. In terms of performance, the maximum read speed is 95MB/s (256GB model), and the maximum write speed is 10MB/s (or higher, depending on capacity). The working temperature range is -25 ° C to 85 ° C.

Comparison of microSD card technical specifications

Product Edge microSD A1 microSD Standard microSD (Class 10) Standard microSD (Class 4)

Capacity 32GB -128GB (with 256GB and 200GB models available) 256GB, 200GB 8GB -128GB 8GB -64GB

Speed Class UHS-I U3 UHS-I U1/Class 10 UHS-I Class 4

Typical read-write (MB/s) 80/50 95/10 (256GB) or 80/10 40/10 20/5

NAND technology 3D NAND 12nm plane? 12nm 12nm

Working temperature -25 ° C~85 ° C -25 ° C~85 ° C -25 ° C~85 ° C -25 ° C~85 ° C

Main applications include monitoring, driving recorders, unmanned aerial vehicles, smartphones, internal storage expansion, universal storage, and basic storage

Note: Edge microSD uses 3D NAND for some capacity, while A1 card may use 12nm planar NAND (as indicated in the original text).

In depth interpretation of core technologies

1. e.MMC interface and HS400 mode

e. MMC is an embedded storage interface defined by the JEDEC standard, which integrates MMC interface, NAND flash memory, and controller into one package. HS400 (High Speed 400) is a double data rate mode defined by e.MMC 5.0/5.1, providing a theoretical interface speed of up to 400MB/s on an 8-bit bus. INAND 7350 and 7232 support HS400, ensuring compatibility with mainstream mobile application processors.

2. SmartSLC technology

SmartSLC is a dynamic storage conversion technology. Normally, NAND flash memory operates in TLC (3 bits per cell) or MLC (2 bits per cell) mode to reduce costs. When high-speed writing is required (such as recording 4K videos), SmartSLC temporarily switches some capacity to SLC mode (1 bit per unit), which can increase the writing speed several times. After the writing is completed, the data is rewritten back to the TLC/MLC area in the background. The second generation SmartSLC further optimizes conversion efficiency and lifespan management, making iNAND 7232 an ideal choice for mobile video creation.

3. 3D NAND flash memory

Traditional 2D NAND increases density by reducing the manufacturing process, but faces issues of leakage and interference. 3D NAND stacks storage units vertically, such as 32 layers, 64 layers, or even higher. The iNAND 7350 and Edge microSD cards use 3D NAND, which not only achieves a high capacity of 256GB, but also improves write durability and read interference tolerance, while reducing the cost per GB.

4. Application performance level A1

The A1 symbol introduced by the SD 5.1 specification aims to address the issue of insufficient random I/O performance when microSD cards were used as internal storage in the past. A1 requires a minimum of 1500 IOPS for random reads and 500 IOPS for random writes. The SanDisk A1 card meets this standard, allowing phone manufacturers to confidently design microSD card slots for expandable internal storage without sacrificing the smoothness of application startup and operation.

Application Scenarios and Selection Guidelines

mobile device

Flagship phone/tablet: Choose iNAND 7350 (256GB) for maximum capacity and fastest read-write, supporting high frame rate gaming and 4K video editing.

Mid end mobile phone: iNAND 7232 provides balanced capacity and video recording performance, or uses A1 microSD card as expandable internal storage.

Entry level phone: iNAND 7250 (8-64GB) paired with A1 microSD card for an acceptable experience at the lowest cost.

Industrial and Embedded Systems

Industrial control panel, HMI: iNAND 7250 wide temperature design (-25 ° C~85 ° C), ensures stable operation in the factory environment.

In car infotainment: iNAND 7250 or 7350 (depending on temperature requirements), paired with Edge microSD card for map data storage.

Monitoring and edge computing

Security camera: Edge microSD card supports U3/V30, continuous writing without frame drop, and 3D NAND ensures erase life.

Driving recorder: Edge microSD (-25 ° C~85 ° C) can withstand high temperatures inside the car, and 64GB can record several hours of loop videos.

Drone aerial photography: Edge microSD with high capacity (256GB) stores 60 hours of Full HD video, meeting long-term tasks.

Consumer electronics peripherals

Gaming handheld consoles and tablets: The A1 microSD card can be used as an internal storage extension to install large games and applications.

Digital camera: Edge or A1 card is suitable for high bitrate video recording.

Ecological Cooperation and Standardization

SanDisk collaborates closely with device manufacturers, operating system suppliers, mobile network operators, system integrators, chipset providers, and application developers to optimize the iNAND embedded flash product portfolio for next-generation devices. For example, conducting compatibility testing with chip manufacturers such as Qualcomm and MediaTek to ensure the performance of iNAND on Snapdragon and Dimensity platforms. Meanwhile, SanDisk's active participation in JEDEC (defining e.MMC/UFS standards) and SD Association (defining microSD standards) has enabled it to proactively lay out new technology specifications, such as the evolution from e.MMC 5.0 to 5.1, and the definition of A1/A2 application performance levels.

Ordering information and packaging precautions

The document provides examples of ordering codes for some iNAND models:

iNAND 7350: SDINBDD4-32G (32GB), SDINBDD4-64G, SDINBDD4-128G, SDINBDD4-256G

iNAND 7232: SDINADF4-32G-L/H (32GB), 64G, 128G

iNAND 7250: SDINBDG4-8G (8GB), 16G, 32G, 64G

The microSD card model starts with SDSDQ, with different suffixes representing different speed levels and capacities. In terms of packaging, all iNAND products are small VFBGA packages measuring 11.5mm x 13mm, with a thickness controlled within 1.2mm, suitable for ultra-thin device design. Design engineers should refer to the latest data manual to confirm the pin layout and soldering temperature curve.