JEDEC defined the endurance rating TBW (TeraByte Written) for indicating the number of terabytes an eMMC can be written. This is an approximation of an eMMC’s expected lifespan. To calculate the TBW of an eMMC, the following equation is applied:

• TBW = [(NAND Endurance) x (eMMC Capacity)] / WAF

NAND Endurance:

• NAND endurance refers to the P/E (Program/Erase) cycle of a NAND flash.

eMMC Capacity:

• The eMMC capacity is the specific capacity in total of an eMMC.

Write Amplification Factor (WAF) is a numerical value representing the ratio between the amount of data that an eMMC controller needs to write and the amount of data that the host’s flash controller writes. A better WAF, which is near 1, guarantees better endurance and lower frequency of data written to flash memory. The equation to calculate the WAF is:

• WAF = (Lifetime write to flash) / (Lifetime write to host)

Note: TBW will vary based on usage pattern. Actual customer workload conditions can significantly impact this approximation. Please Contact Us to discuss your application. Additional details regarding write endurance are available upon request.