- Stub Series Terminated Logic
Stub Series Terminated Logic (SSTL) devices are a family of electronic devices for driving
transmission lines. They are specifically 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 ExpressPHYs and other high-speed devices.
Three 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
*SSTL_18, 1.8 V, defined in EIA/JESD8-15
All SSTL voltage specs reference a voltage that is exactly VDDQ/2. For example, the VREF for an SSTL_18 signal is exactly 0.9 Volts.
Terminations can be:
*Class I (one series resistor at the source and one parallel resistor at the load)
*Class II (one series resistor at the source and two parallel resistors, one at each end).
*Class III (asymmetrically parallel terminated)
*Class IIII (asymmetrically doubly parallel terminated)
High-Speed Transceiver Logic- HSTL
* [http://www.jedec.org/download/search/jesd8-9b.pdf JEDEC SSTL_2 Standard]
* [http://www.jedec.org/download/search/JESD8-15a.pdf JEDEC SSTL_18 Standard]
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