Power Loss Protection (PLP)

The Power-Loss Protection (PLP) is a scheme to protect data from loss during a sudden power off when SSD drive is under programming or writing. The function helps secure the integrity of data during power sudden off by adding Extra Power in the circuitry. It is also a technology designed to protect data from being corrupted or erased from an SSD when power is abruptly cut off. The sudden power loss may result from a power outage, power surge, or a power cord accidentally pulled out from a power outlet.

 In the event of sudden power loss, an SSD with PLP protects data by providing power long enough for data to be properly stored and journaled. The emergency charge comes from charged supercapacitors onboard the SSD. The charge only lasts for a very short time (milliseconds) but is adequate to transfer all the data stored in DRAM cache to NAND.

 The PLP mechanism is based on the firmware design that is commonly used in SSDs while it is a hardware and software design for industrial and enterprise-class SSDs. This helps provide more effective power down data protection to prolong the SSD operating times after power down. When the system is properly shut down, the Host end will issue a command to the SSD controllers to notify the subsequent power interruption, which allows the response time for SSD to refresh cache and revise Mapping Table while saving the data temporarily stored in DRAM to NAND Flash.

 For many remote applications, they run under unstable power conditions. This may cause the system to crash at boot and shutdown and potentially damage SSD. PLP function can protect  SSD from power instability that can affect the system. It will ensure the system is stable and the data in the DRAM will be flushed to NAND. It needs to have controller firmware support first with additional power source from PCBA as backup power.

 When the controller detects the power is dropping to a certain level, the controller would inform the host and stop the host from sending more data. The second step is to flush the data in the DRAM into the NAND flash. Since DRAM cannot work when power is off, it would need extra power generated from Polymer Tantalum capacitors add-on PCBA to hold up several mini seconds to ensure the data is flushed out to NAND completely. Currently UDinfo provides three types of PLP function, users can choose according to their needs and cost target.