English
Language : 

LP2996 Datasheet, PDF (14/18 Pages) National Semiconductor (TI) – DDR Termination Regulator
୅දతͳΞϓϦέʔγϣϯճ࿏ ( ͖ͭͮ)
FIGURE 9. DDR-II Termination with higher voltage rails
Ϩϕϧɾγϑτ
SSTL-3 ͳͲɺSSTL-2 Ҏ֎ͷελϯμʔυʹద༻͢ΔͨΊʹɺ
VDDQ ʹରͯ͠ 0.5 ഒҎ֎ͷ܎਺Ͱग़ྗిѹͷϨΪϡϨʔγϣϯ
Λߦ͍͍ͨ৔߹͕͋Γ·͢ɻ܎਺Λม͑ͯ೚ҙͷిѹΛಘΔʹ͸
͍͔ͭ͘ͷํ๏͕͋Γ·͢ɻͦͷ 1 ͭ͸ɺVTT ͔Β VSENSE ୺ࢠ
ؐؼʹ఍߅Λ௥Ճͯ͠ɺग़ྗͷϨϕϧɾγϑτΛߦ͏ํ๏Ͱ͢ɻ
͜ͷํ๏Λ༻͍ͨճ࿏Λ Figure 10ɺ11 ʹࣔ͠·͢ɻ Figure 10
͸ɺ2 ݸͷ௥Ճ఍߅Λ࢖ͬͯɺ಺෦ϦϑΝϨϯεిѹ VDDQ/2 ΑΓ
΋ߴ͍ిѹʹϨϕϧɾγϑτ͢Δճ࿏Ͱ͢ɻVTT ͷਖ਼֬ͳిѹ͸
࣍ͷ͔ࣜΒٻΊΒΕ·͢ɻ
VTT ʹ VDDQ/2 ( 1 ʴ R1/R2)
FIGURE 10. Increasing VTT by Level Shifting
ʹٯɺ఍߅ R2 Λ VSENSE ͱ VDDQ ͷؒʹஔ͚͹ɺVTT ग़ྗΛ
಺෦ϦϑΝϨϯεిѹ VDDQ/2 ΑΓ΋௿͘Ͱ͖·͢ɻVTTͱ఍߅ͷؔ
܎͸࣍ͷࣜͰද͞Ε·͢ɻ
VTT ʹ VDDQ/2 (1 ʵ R1/R2)
www.national.com/jpn/
FIGURE 11. Decreasing VTT by Level Shifting
14