Presentation on theme: "Toshiba America Electronic Components, Inc. November 2003"— Presentation transcript:
1Toshiba America Electronic Components, Inc. November 2003 Chip Enable Don’t Care NAND – Enabling Higher Performance, High Density NAND Flash Memory for Cellular Handset ApplicationsToshiba America Electronic Components, Inc.November 2003Engineers of today’s feature-rich cell phones are finding multiple design challenges. To support these auxiliary and multimedia processing capabilities, they need a memory subsystem that is higher density and higher performance and ideally, lower cost. They also need a flexible solution that can accommodate low, mid and high-end configurations without major changes to the overall phone design. Today I’m going to speak with you about:Memory density trends in cell phonesMemory requirements in next-generation cell phonesIdentify the different memory architecturesThe trade-offs with each and advantages by applicationHow packaging innovations are important design considerationsAnd tips for selecting the optimal memory subsystem for a specific application
2Chip Enabled “Don’t Care” NAND Modified NAND Flash for easier integration in cell phones or other CE devices with complex memory subsystems.Targeted to address growing file storage requirements in cell phonesConventional NAND flash requires that the chip enable signal line be asserted low during the entire read cycle which prevents the processor from communicating with other devices on the same busChip Enable “Don’t Care” NAND flash allows the microprocessor to communicate with other devices on the bus such as SRAM, PSRAM or NOR flash while the NAND retrieves the information requested.Enables easier integration of NAND with NOR, SRAM and PSRAM in a systemInitially available in 128Mb (TC581282AXB) and 256Mb (TC582562AXB) densities (.16 micron). New part numbers after die shrink to 0.13 micron in Q are TC58DDM82A1 (256Mb, 1.8V core and I/O) and TC58DDM82A1 (256Mb, dual power 2.5V to 3.6V for VCC and 1.65V to 1.85V for VCCQ).CEDC feature also now available in large block NAND in densities of 1Gb and 2Gb
3MCP Memory Subsystem Trend Conventional “Talk-only” Cell phones used NOR + SRAM for code storage, backup and data storage memory requirementsAs cell phone applications have increased, the need for increased data storage for music, photo and data storage, as well as additional software application storage has made NAND Flash more attractive because of its faster program and erase times, higher density and smaller cell size.Chip Enable Don’t Care NAND makes NAND flash much easier to combine with NOR and other types of memory in memory subsystems (or multi-chip packages) with multiple types of memoryCEDC NAND can be used in conventional cell phone architectures which combine NOR+SRAM+NAND or in newer NAND + low power SDRAM architectures.NOR+SRAM+NAND MCP solutions are rapidly gaining in acceptance among cell phone manufacturers
5Memory Requirements for Cellular Phones 64M-128MLarge DensityHigh SpeedLow CostLow PowerRAMMovie / MusicBufferWorking AreaPSRAMLP SDRAM16M-32M8M-16M8M-16MData Backup8M-16MLow PowerLP-SRAM4M-8MMCPTalk only Browse phone G16M32M-64M64M-128M128M-256MHigh SpeedBoot &Basic ProgramNORCellular phone memory requirements have become increasingly complex to support the additional features and applications that are now included. Cell phones have evolved from talk-only phones that needed only 4 – 8 Mb of low-power SRAM for data storage with 16Mb of NOR for code storage. Now, more complex phones need 8Mb to 16Mb of low-power SRAM for data backup, 32Mb to 128Mb Pseudo-SRAM (PSRAM) for program/movie/music working area; 128Mb to 256Mb high speed NOR for bootable code storage on basic phone programs, and 128Mb to 256Mb or more additional memory, often NAND Flash, for application software and storage.NAND flash is becoming popular because it is offered at a much lower cost-per-bit and with much higher Data Write/Erase performance. Recently cell phone designs have started using NAND flash plus low-power SDRAM combinations that enable a low-cost, high-capacity and high-performance solution.128M-512MLarge DensityLow CostHigh SpeedprogramFlashMovie / MusicApp. SoftStorageNAND
6Application Trend and Onboard Memory Size This is the trend of cell phone features in Japanese cell phone carrier.The rate at which designers are opting to add multiple applications is also growing at a much faster rate. A cellular phone with multimedia and digital camera functionality will need upwards of 144Mb of RAM with 512Mb of Flash memory. What also compounds and impacts memory capacity is the growing number of applications that cellular subscribers are demanding. Initial auxiliary applications such as and web browsing are being replaced by JAVA applications for downloading or more complex multimedia functions for movie, camera and music playback. As you can see from the trend line on the right side, the number of new phones that include digital camera capability is expected to increase rapidly over the next year or two.Memory size is increased by diversity of application .
7Multi-Chip Package for Mobile Phone Demand from Mobile Phone MarketMCP SolutionLow cost solutionEmbedded High-Density NAND(128M/256M/512M +)High-Density Pseudo SRAM(32M/64M/128M)Demand of large densityRAM and Flash.Increase of various applicationHigh-speed requirement for execution of application software(PSRAM/NOR)＋High-Speed Function (PSRAM/NOR)8Page Mode: 25ns→18nsBurst Mode 15nsTradeoffs in density, speed, cost and power make combinations of several different types of memory desirable for cell phones. To address the various requirements, semi-custom combinations of two, three and four types of memory, packaged in a compact multi-chip package are needed to meet the demands for next-generation, multi-functioning phones.Multi-chip packages combine a complete, complex memory subsystem in a single, small component
8Architectures for next generation phones Conventional solutionCode : NORWork : Pseudo-SRAMData : NANDBackup : SRAM (in Japanese market)with burst modeCost oriented solutionCode & Data : NANDWork : LP-SDRAMwith shadowingarchitectureThe conventional memory architecture for today’s multi-function cellular phones typically uses NOR Flash for code storage, PSRAM for work space, NAND Flash for data storage and in some markets, SRAM for backup. Today, designers build upon the conventional cell phone memory architecture by increasing density of the NOR and PSRAM, and adding NAND Flash for data storage. And memory vendors have started to support Burst NOR and Burst PSRAM to improve performance of system.A newer approach well suited to 3G phones with advanced features used higher density, lower cost NAND with low power SDRAM in a shadowing architecture to provide a cost effective solution that can offer performance advantages due to the faster bus speed of the SDRAM.
9Mobile MCP Memory Trend > 90%CameraPhones2001< 10%CameraPhonesMP/YSDRAM+NANDProduction volumeNAND+NOR+RAMNOR＋RAM ・新たなMCPとしてSDRAM+NANDのMCPが03年より現れ、ｼｬﾄﾞｳｲﾝｸﾞに適したｿﾌﾄｳｪｱが普及するに従って、05年：８％、06年：２０％、07年：３７％と増加 ・NANDの搭載比率は05年には半数超えの５７％、その後も増加。 ・東芝が売りとする多種・多段のメモリ構成の従来MCPは新MCPの存在とともに減少傾向ではあるが、07年でも ６３％は残る。しかし、昨今の高性能化でPSRAM/NORのBurst機能は必要。CY From 2003, NAND becoming popular in Europe and US (already popular in Asia) driven by storage requirementsSource: Toshiba Internal Data/Projections
10Trend of Multi-Chip Package more7Chip over5/6Chip St-MCP1.61.69x123/4Chip St-MCP(NOR+NOR+SRAM+PSRAM)Stacked MCP9x121.49x121.49 x 12(SRAM+NOR)(NAND+NOR+PSRAM)9x121.4(4MS+32MF)9x121.43ChipPackage Area0.8mm pitch9x12(16MS+64MF)Small69 balls (Actual 56balls)9x121.21.27x104Chip1.47x103Chip1.27 x 10Small form factorPackaging advances today make it possible to create MCPs that stack up to 6 chips with different memory types into a single BGA package.7x101.2(8/4MS+64/32MF)20002001200220032004CY
115-chip Stacked-MCP Technology TOSHIBA 5Chip St-MCPChip5Chip4Chip3Chip2Chip11.6mm MaxWIRE BONDPKG SIZE9x127x10Chip1Chip2Chip3Chip4Chip5Innovations in miniaturization and thinner packages, combined with die shrinks have made this stacking technology possible. Toshiba uses a revolutionary new wire bond technique that further aids in stacking multiple chips. As handsets continue to shrink, MCPs are a necessity to integrate a complete, complex memory subsystem into a single small package.
12NAND / NOR Characteristics 3V, 1.8Vx8/x1650ns(serial access cycle)25ms(random access)200ms/512Byte2ms/Block (16KB)33.6ms / 64KB (x8)~ 1GbitNOR~ 128Mbit3V, 1.8Vx8/x1670ns(30pF, 2.3V)65ns(30pF, 2.7V)8ms/Byte4.1ms/512Byte700ms/Block1.23s/Block (main:64KB)CapacityPower SupplyI/OAccess TimeProgramSpeed (typ.)Erase Speed(typ.)Prog+Erase(typ.)This slide compares the major characteristics of NAND and NOR. NAND flash is currently available in densities 8 times greater than NOR. NAND also offers much faster programming and erase times, a small block size and requires less space because of its small cell size. On the other hand, NOR flash offers a slight advantage in random access times, because NOR Flash has a fully random access interface.But data in system, application program, image data and so on, usually is sizable, then sequential read of NAND Flash with 25 micro seconds initial delay, is enough for system’s requirement.And a difference in combined programming and erase time of 33 milliseconds for NAND and over 1 second for NOR is large enough to be detected by the user.
134F2 10F2 NAND vs. NOR - Cell Structure NAND NOR Cell Array Layout ２Ｆ4F2NANDSource lineWord lineUnit CellNORBit lineWord lineContactCellArrayUnit CellSource line５Ｆ２ＦLayoutOne of the most important characteristics of memory in a consumer electronics application is the bit cost. In the case of a semiconductor memory, the bit cost is dependent on the memory cell area per bit. Since the cell area of NAND Flash is smaller than the cell area of NOR Flash, NAND Flash offers the potential to be less expensive than NOR Flash.NOR Flash achieves random access by connecting the memory cells to the bit lines in parallel.Cross-sectionCell size10F2
16SummaryMemory requirements in high-end cell phones have increased dramatically to support new applicationsDifferent types of memory are best suited for different applicationsCode storageWorking memoryFile and additional application storageMulti-chip packages (MCP) enable complex memory subsystems in a single componentTraditional NOR +SRAM memory solutions for cell phones are being replaced by NOR+PSRAM+NAND and other combinations of multiple memoriesOne newer low-cost alternative is NAND + Low Power SDRAMChip Enable Don’t Care NAND Flash makes integration of NAND with other memory types much easier.In summary, the market for high-end cell phones has increased and so have the memory requirements to support new features and applications.Tradeoffs in density, speed, cost and power make combinations of different types of memory necessary for code storage, working memory and file and additional application storage.Because space is at a premium with the shrinking of the handset, multi-chip packages enable the creation of a complex memory subsystem in a single component.To save space and cost, traditional NOR and SRAM solutions are being replaced by NOR, Pseudo SRAM and NAND as well as other combinations that suit specific applications.For higher performance that supports many additional features, a newer low-cost alternative is NAND plus Low Power SDRAM.When selecting the optimal configuration for a cell phone memory subsystem, designers must evaluate how to balance the tradeoffs in cost, performance, power consumption and density to best fit the requirements of a specific design.
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