View source for Stub Series Terminated Logic

{{Short description|Electrical standards}}
'''Stub Series Terminated Logic''' ('''SSTL''')  is a group of electrical standards for driving [[transmission line]]s commonly used with [[DRAM]] based [[Double data rate|DDR]] memory IC's and memory modules. SSTL is primarily designed for driving the [[DDR SDRAM|DDR (double-data-rate) SDRAM]] modules used in [[computer memory]]; however, it is also used in other applications, notably some [[PCI Express]] PHYs and other high-speed devices.<ref>Jaci Chang ''Design Considerations for the DDR3 Memory Sub-system''. Jedex, 2004, p. 4. http://www.jedex.org/images/pdf/samsung%20-%20jaci_chang.pdf</ref>

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 [[Double data rate|DDR]] among other things.
*SSTL_18, 1.8 V, defined in EIA/JESD8-15A, used in [[DDR2 SDRAM|DDR2]] among other things.
*SSTL_15, 1.5 V, used in [[DDR3]] among other things.

SSTL_3 uses a reference of 0.45 * VDDQ (1.5 V).  SSTL_2 and SSTL_18 reference a voltage that is exactly VDDQ / 2 (1.25 V and 0.9 V respectively).<ref>Tom Granberg ''Handbook of Digital Techniques for High-Speed Digital Design''.  Pearson Education, 2004, p. 160-161.</ref>

SSTL_3 and SSTL_2 support two termination classes (50 ohm or 25 ohm load). SSTL_18 only supports one (25 ohm load).

==See also==
*[[High-Speed Transceiver Logic]] - HSTL

==References==
{{Reflist}}

== External links ==
JEDEC homepage links; require (free) login:
* [http://www.jedec.org/sites/default/files/docs/JESD8-9B.pdf JEDEC SSTL_2 Standard (JESD8-9B)]
* [http://www.jedec.org/sites/default/files/docs/JESD8-15A.pdf JEDEC SSTL_18 Standard (JESD8-15A)]


[[Category:Computer memory]]
[[Category:JEDEC standards]]


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