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LP2996 Datasheet, PDF (16/18 Pages) National Semiconductor (TI) – DDR Termination Regulator
୅දతͳΞϓϦέʔγϣϯճ࿏ ( ͖ͭͮ)
FIGURE 14. Typical SSTL-2 Application Circuit for Motherboards
Ұൠͷ PC ΞϓϦέʔγϣϯͰ͸ɺϞδϡʔϧʹ࣮૷͞Εͨ DDR-
SDRAM DIMM ʹΑͬͯ௕͍ΠϯλʔίωΫτ͕ੜ͡ΔͨΊɺଟ਺
ͷσΧοϓϦϯά͕ඞཁͰ͢ɻͦͷͨΊɺ௨ৗ 1000ЖF ͷ༰ྔൣ
ғͷΞϧϛిղίϯσϯαΛόϧΫɾίϯσϯαͱͯ͠࢖༻͠·͢ɻ
PCB ઃؔ͢ʹܭΔߟྀ
1. ύϫʔɾϨʔϧͷೖྗίϯσϯα͸ɺՄೳͳݶΓ PVIN ୺ࢠͷ
ۙ͘ʹ഑ஔ͍ͯͩ͘͠͞ɻ
2. VSENSE ୺ࢠʹ͸ɺVTT λʔϛωʔγϣϯ͞ΕΔόεͷϨΪϡϨʔ
γϣϯ͕ඞཁͳ఺ʹ઀ଓ͍ͯͩ͘͠͞ɻϚβʔϘʔυɾΞϓϦέʔ
γϣϯͰ͸λʔϛωʔγϣϯɾόεͷத఺͕ཧ૝తͰ͢ɻ
3. VDDQ ೖྗ͸ɺDIMM ·ͨ͸νοϓηοτͷ VDDQ ʹݯిର͠
ͯϦϞʔτɾηϯεͱͳΔΑ͏ʹ઀ଓ͠·͢ɻ ಺෦ϦϑΝϨϯεి
ѹΛ࠷΋ਫ਼౓ߴ͘ੜ੒Ͱ͖ΔΑ͏ʹͳΓ·͢ɻ
4. ೤ಛੑΛվળ͢Δʹ͸ɺύοέʔδ͔Βͷ์೤ྔΛ૿΍ͨ͢Ί
ʹද໘૚ͷಔഩΛେ͖͍ͯͩ͘͘͠͞ɻάϥ΢ϯυ഑ઢͱ಺෦ά
ϥ΢ϯυɾϓϨʔϯΛ઀ଓ͢Δଟ਺ͷϏΞ΋์೤Λॿ͚·͢ɻ͞
Βʹɺ੡଄ج४ͱͯ͠ڐ༰͞ΕΔͷͰ͋Ε͹ɺϏΞ͸ύοέʔ
δԼ෦ʹ΋഑ஔ͍ͯͩ͘͠͞ɻ
5. VSENSE ৴߸ͷ഑ઢઃͰܭ͸ɺεΠονϯά͢Δ I/O ৴߸͔Β
ϊΠζΛरΘͳ͍Α͏ʹ஫ҙ͕ඞཁͰ͢ɻ VSENSE ୺ࢠͷۙ͘
ʹ 0.1ЖF ηϥϛοΫɾίϯσϯαΛஔ͘ͱɺ޷·͘͠ͳ͍ߴप೾৴
߸ΛϑΟϧλϦϯάͰ͖·͢ɻ VSENSE ഑ઢ͕௕͍৔߹ɺͱ͘ʹ
ݕ౼Λཁ͠·͢ɻ
6. VREFʹ͸ϨΪϡϨʔγϣϯੑೳͷվળͷͨΊɺ0.1ЖF ʙ 0.01ЖF
ͷηϥϛοΫɾίϯσϯαΛ઀ଓͯ͠ϊΠζΛόΠύεͯͩ͘͠͞
͍ɻίϯσϯα͸ VREF ୺ࢠͷՄೳͳݶΓۙ͘ʹ഑ஔͯͩ͘͠
͍͞ɻ
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