Stub Series Terminated Logic
Encyclopedia
Stub Series Terminated Logic (SSTL) is a group of electrical standards for driving transmission line
s commonly used with DRAM
based DDR
memory IC's and memory modules . Primarily designed for driving the DDR (double-data-rate) SDRAM
modules used in computer memory
. However, they are 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(1.5V). SSTL_2 and SSTL_18 reference a voltage that is exactly VDDQ/2(1.25V and .9V respectively).
SSTL_3 and SSTL_2 support two termination classes(50 ohm or 25 ohm load). SSTL_18 only supports one(25 ohm load).
Transmission line
In communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
s commonly used with DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
based DDR
DDR
DDR may refer to:In entertainment:*Dance Dance Revolution, a music video game series by Konami*DDR , a Norwegian rock band singing in German.*DDR , a Greenlandic punk band singing in Danish.In organizations:...
memory IC's and memory modules . Primarily designed for driving the DDR (double-data-rate) SDRAM
DDR SDRAM
Double data rate synchronous dynamic random access memory is a class of memory integrated circuits used in computers. DDR SDRAM has been superseded by DDR2 SDRAM and DDR3 SDRAM, neither of which are either forward or backward compatible with DDR SDRAM, meaning that DDR2 or DDR3 memory modules...
modules used in computer memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
. However, they are also used in other applications, notably, some PCI Express
PCI Express
PCI Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP bus standards...
PHYs and other high-speed devices.
Four voltage levels for SSTL are defined:
- SSTL_3, 3.3 V, defined in EIA/JESD8-8 1996
- SSTL_2, 2.5 V, defined in EIA/JESD8-9B 2002 used in DDRDDRDDR may refer to:In entertainment:*Dance Dance Revolution, a music video game series by Konami*DDR , a Norwegian rock band singing in German.*DDR , a Greenlandic punk band singing in Danish.In organizations:...
among other things. - SSTL_18, 1.8 V, defined in EIA/JESD8-15, used in DDR2DDR2DDR2 may refer to:* DDR2 SDRAM, the computer memory technology* Dance Dance Revolution 2ndMix, the video game* DDR2 , a human gene...
among other things. - SSTL_15, 1.5 V, Used in DDR3 among other things.
SSTL_3 uses a reference of .45*VDDQ(1.5V). SSTL_2 and SSTL_18 reference a voltage that is exactly VDDQ/2(1.25V and .9V respectively).
SSTL_3 and SSTL_2 support two termination classes(50 ohm or 25 ohm load). SSTL_18 only supports one(25 ohm load).