Stub Series Terminated Logic


Stub Series Terminated Logic is a group of electrical standards for driving transmission lines commonly used with DRAM based DDR memory IC's and memory modules. SSTL is primarily designed for driving the DDR SDRAM modules used in computer memory; however, it is also used in other applications, notably some PCI Express PHYs and other high-speed devices.
Four voltage levels for SSTL are defined:
SSTL_3 uses a reference of.45*VDDQ. SSTL_2 and SSTL_18 reference a voltage that is exactly VDDQ/2.
SSTL_3 and SSTL_2 support two termination classes. SSTL_18 only supports one.