Embedded Computing Design October 2011 : Page 13Silicon SPECIAL ADVERTISING FEATURE THE SOLUTION FOR SUDDEN POWER DOWN IN NAND FLASH MODULES/DRIVES By Alex Tseng, Product Manager, ATP Electronics The unstable power conditions of outdoor applications such as telecommunications/networking and embedded systems run the risk of data loss and drive corruption during a sudden power failure. Power failures result in downtime as embedded systems are reformatted and operating systems are reinstalled. Furthermore, overall productivity decreases as cost of ownership increases for industrial-grade memory solutions, which are specifically designed for reliability in all conditions for mission-critical applications. NAND flash solid-state drives and embedded modules offer superior reliability and power consumption from traditional rotating media. Flash controllers typically utilize internal volatile SRAM data buffers and are thus susceptible to data corruption under sudden power down. A power backup function is required to sustain these active compo-nents and completely prevent mid-transfer data loss. Battery-based active power backup Battery-based solutions are not ideal for any embedded applications due to their need for replacement over time and are not an acceptable solution due to the high cost of in-field maintenance. Supercap-based active power backup Supercaps offer sustained power to vital components allowing for completion of controller and flash func-tions, but due to certain limitations are not suitable for industrial applications. Supercaps are well known for their sensitivity to temperature change and their ten-dency to lose capacitance and functionality at extreme temperatures. Supercaps, like batteries, also cannot be i mplemented in small form factor embedded modules due to space requirements. Tantalum capacitor-based active power backup example: ATP PowerProtector The solid-state capacitor is a critical component that surpasses the natural limitations of existing supercap designs. The solid-state capacitor’s low series resistance SOLUTION Tantalum cap Supercap Battery DESIGN Minimal space required Moderate space required Larger space required EFFECTIVENESS Good Good Good Silicon and minimal sensitivity to temperature and humidity make it the ideal solution for extreme situations. In addition, the minimal space requirements of Tantalum capacitors allow for implementation in small form factor embedded mod-ules. Table 1 compares the Tantalum capacitor with the other technologies available for sudden power down. [Table 1 | Comparison of available technologies for sudden power down situations] PowerProtector is a stand-alone hardware design that does not require specific controllers or customized firm-ware. ATP PowerProtector’s stand-alone hardware design ensures a sufficient amount of reserve power during any power abnormalities such as unstable voltages and power outages. A backup power circuit ensures reliable controller and NAND flash operation during a power failure. During a sudden power failure, the abnormality is discov-ered by a power loss detection circuit that is integrated into the drive, activating PowerProtector. The drive then draws power from PowerProtector’s solid-state capacitors for reserve power, guaranteeing reliable drive operation. The solid-state capacitors allow the flash to finish processing the last command or data. The lifespan of an industrial-grade product is a critical feature to consider, given that most products last more than five years. The average lifespan of supercap is less than two years; the capacitance will degrade over time and eventually fail to perform. In contrast, the solid-state capac-itor of PowerProtector has an average lifespan of more than five years and no capacitance degradation. Three actions that a drive typically performs are read, write, and erase. Under a sudden power failure, data integrity is usually not harmed if the drive is in the read process. However, this is not the case if the drive is in write or erase mode, and this is where PowerProtector can be advanta-geous in keeping critical data protected. ATP Electronics www.atpinc.com RISK Low Degradation Frequent replacement LIFESPAN >5 yrs <2 yrs <3 yrs WIDE TEMPERATURE Yes No No Table 1 | Comparison of available technologies for sudden power down situations www.embedded-computing.com Embedded Computing Design October 2011 | 13 ATP Electronics |
