Solid State Drives (SSD) have begun targeting the enterprise server and notebook market, replacing the traditional hard-disk drives. SSDs target higher read/write performance, higher reliability and lower power consumption than their mechanical predecessors. Key performance vectors of SSDs are: Write Endurance/Performance, Error/Defect Rates, and Data Security. However design challenges also include size and heat dissipation reductions.
Power Supply Efficiency and Heat:
Heat and heat tolerance is a key concern in device selection for SSDs, especially considering that the drives may be used in RAIDs, or Notebook PCs, which have a significant power dissipation on their own. A typical SSD may draw 2-4 A for normal operation, however, unlike the incremental increases in power demand for a hard-disk drive when capacity increases, an SSD’s power consumption increases fairly linearly as memory increases.
Not only will a lower noise, higher efficiency power supply increase the lifespan of the SSD by reducing the heat of the environment, it can also decrease the number of erroneous rewrites by providing more stable voltage rails for the Flash and NAND memory cells. It is important to select solutions that have good efficiency at both full loads and light loads since the drive may spend most of its time in standby. At the same time, power solutions the ramp up and become stable quickly, without over shooting the regulation voltage allow the drive to wake up, accept data and go back into standby in shorter time spans, further reducing the heat in the drive.
SSD Interfaces:
For Internal drives SATA is the common interface. First generation had a maximum transfer rate of 150 MBps, and second generation supports up to 300 MBps. The Interface drivers are typically designed into the core chips set of the drive. However, some implementations may require redrivers to extend SATA trace/cable distance. Typically redrivers are used on the host side, although they can be used in adapter card applications or within the SSD. Additionally, is the Drives are removable, considerations may need to be made for ESD protection or transient suppression on all connections.
External SSDs may interface with the PC via a SATA adaptor, or could leverage the USB interface. Given the 2.5 W limit, USB would not provide enough power for the drive, so an AC/DC power adaptor would need to be used.
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