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LP2996 Datasheet, PDF (15/18 Pages) National Semiconductor (TI) – DDR Termination Regulator
୅දతͳΞϓϦέʔγϣϯճ࿏ ( ͖ͭͮ)
HSTL ΞϓϦέʔγϣϯ
LP2996 ͸ɺVDDQ ʹ 1.5V ϨʔϧΛ઀ଓ͢Δ͚ͩͰɺ؆୯ʹ
HSTL ΞϓϦέʔγϣϯʹద༻Ͱ͖·͢ɻλʔϛωʔγϣϯ఍߅ʹ༩
͑ΒΕΔ VTT ͱ VREF ిѹ͸͓Αͦ 0.75V ʹͳΓ·͢ɻ ࠷దͳੑ
ೳΛಘΔͨΊʹ AVINͱPVIN ͸ 2.5VϨʔϧʹ઀ଓ͍ͯͩ͘͠͞ɻ
FIGURE 12. HSTL Application
QDR ΞϓϦέʔγϣϯ
ΫϫουɾσʔλɾϨʔτ (QDR) ΞϓϦέʔγϣϯ͸ߴ͍ϝϞϦੑೳ
ΛಘΔͨΊʹෳ਺ͷνϟωϧΛ࢖༻͠·͢ɻͦͷͨΊόε৴߸ઢ
਺͕૿͑ɺλʔϛωʔγϣϯʹඞཁͳిྲྀϨϕϧ΋େ͖͘ͳΓ·͢ɻ
ͦ͜ͰλʔϛωʔγϣϯͰ͸ɺෳ਺νϟωϧͷ֤νϟωϧ͝ͱʹݸผ
ͷ LP2996 Λ࢖༻͢Δ͜ͱΛਪ঑͠·͢ɻج൘ϨΠΞ΢τΛ୯७Խ
Ͱ͖ɺ֤ϨΪϡϨʔλͷ಺෦ফඅిྗ΋཈͑ΒΕ·͢ɻ ֤ϨΪϡ
Ϩʔλ͔Βग़ྗ͞ΕΔݸʑͷ VREF ৴߸Λ֤ DIMM όϯΫʹ༩͑
·͢ɻνοϓηοτ༻ͷϦϑΝϨϯεిѹ͸ɺॴہతʹ఍߅෼ѹΛ
ߦ͏͔ɺLP2996 ͷ͏ͪͷ 1 ͔ͭΒ༩͑·͢ɻ VREF ͸ VTT ʹ௥
ै͢Δ͜ͱ͕·ࠐݟΕɺ·ͨσόΠεؒͷ͹Β͖ͭ͸খ͍ͨ͞Ίɺ
֤ LP2996 ͷϦϑΝϨϯεిѹͷࠩ͸Θ͔ͣͰ͢ɻ
ग़ྗίϯσϯαͷબ୒
LP2996Λ SSTL-2 I/O ৴߸ͷλʔϛωʔγϣϯ༻ʹ࢖༻ͨ͠ΞϓϦ
έʔγϣϯͰ͸ɺFigure 13 ʹࣔ͢୅දతΞϓϦέʔγϣϯճ࿏Λ
ద༻ՄೳͰ͢ɻ
FIGURE 13. Typical SSTL-2 Application Circuit
͜ͷճ࿏͸ɺ࠷খͷج൘໘ੵͱ࠷খͷ෦඼఺਺Ͱλʔϛωʔγϣ
ϯճ࿏Λ࣮͢·͍ͯ͠ݱɻ બ୒͢΂͖ίϯσϯαͷ༰ྔ͸ɺλʔ
ϛωʔγϣϯ͢Δ৴߸ઢ਺ͱ࠷େෛՙిྲྀʹґଘͯ͠ҟͳΓ·͢
͕ɺVTT ͕௕͍഑ઢͰ෼഑͞Ε͍ͯΔϚβʔϘʔυ΍ΞϓϦέʔ
γϣϯͰ͸ɺෳ਺ͷόϧΫɾίϯσϯαΛ࢖༻͠ɺ͞Βʹߴप೾σ
ΧοϓϦϯάɾίϯσϯαΛ௥Ճ͢Δ͜ͱ͕๬·Ε·͢ɻ࣍ͷ Figure
14 ʹɺ2 ݸͷόϧΫग़ྗίϯσϯαΛɺ࠷దͳҐஔͰ͋Δ VTT
૚ͷ྆୺ʹ഑ஔͨ͠ճ࿏ྫΛࣔ͠·͢ɻESR ͕খ͔ͭ͘͞ίετ
͕௿͍େ༰ྔΞϧϛిղίϯσϯαΛ࢖༻͍ͯ͠·͢ɻ
15
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