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LP2996 Datasheet, PDF (11/18 Pages) National Semiconductor (TI) – DDR Termination Regulator
์೤ ( ͖ͭͮ)
FIGURE 4. ВJA vs Airflow Speed (JEDEC Board with 4
Vias)
ВJA ͷ࠷దԽΛߦ͍ɺ͋ΘͤͯपғԹ౓͕௿͍ج൘ྖҬʹ
LP2996 Λ഑ஔ͢Ε͹ɺσόΠεΛΑΓେ͖ͳফඅిྗͰ࢖༻Մ
ೳʹͳΓ·͢ɻ ಺෦ফඅిྗ͸ओʹɺγϯΫ͔ιʔεʹґΒͳ͍
VTT ͷग़ྗిྲྀɺAVIN ͷ଴࣌ػফඅిྲྀɺVDDQ ͷ଴࣌ػফ
අిྲྀͱ͍ͬͨ 3 छྨͷଛࣦͷ߹ٻͯ͠ͱܭΊΒΕ·͢ɻγϟο
τμ΢ϯ͕ LOW Ͱ͸ͳ͍ΞΫςΟϒঢ়ଶͰ͸ɺ಺෦ফඅిྗ͸
࣍ͷࣜͰࢉग़͞Ε·͢ɻ
PD ʹ PAVIN ʴ PVDDQ ʴ PVTT
PAVIN ʹ IAVIN ʷ VAVIN
PVDDQ ʹ VVDDQ ʷ IVDDQ ʹ (VVDDQ)2 ʸ RVDDQ
VTT ͷ࠷େফඅిྗΛٻΊΔ৔߹ɺిྲྀ͕γϯΫ࣌ͱιʔε࣌
ͷ྆ঢ়ଶͰ VTT Λݕ౼͢Δඞཁ͕͋Γ·͢ɻͨͩ͠ VTT ͸γϯ
Ϋͱιʔεͷ྆ํͷঢ়ଶΛಉ࣌ʹ࠾Γಘͳ͍ͨΊɺ߹Ͱܭ͸Ͳͪ
Β͔ 1 ͭͷ஋ͷΈΛՃࢉ͠·͢ɻ
PVTT ʹ VVTT ʷ ILOAD ( γϯΫ࣌ )
PVTT ʹ ( VPVIN ʵ VVTT) ʷ ILOAD ( ιʔε࣌ )
γϟοτμ΢ϯɾεςʔτʹ͋Δ LP2996 ͷফඅిྗ΋ࢉܭՄೳͰ
͢ɻVTT ग़ྗ͸ TRI-STATE ͱͳΓγϯΫిྲྀ΋ιʔεిྲྀ΋ྲྀΕ
ͳ͍ͨΊɺిྗ͍͓֘ͯʹࢉܭ౰߲͸औΓআ͍ͯߟ͑·͢ ( ࿙
Εిྲྀ͸ແࢹͰ͖Δ )ɻγϟοτμ΢ϯத͸ɺ௿͞ݮΕͯ͸͍Δ΋ͷ
ͷ AVIN ͷ଴࣌ػফඅిྲྀͱɺVDDQ ݱʹࢠ୺ΕΔҰఆͷΠϯ
ϐʔμϯεʹΑΓɺएׯͷଛࣦ͕ੜ͡·͢ɻ
PD ʹ PAVIN ʴ PVDDQ
PAVIN ʹ IAVIN ʷ VAVIN
PVDDQ ʹ VVDDQ ʷ IVDDQ ʹ (VVDDQ)2 ʸ RVDDQ
˞ RVDDQ ʹ 50kЊʴ 50kЊ
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