L1087 Datasheet, PDF (3/10 Pages) National Semiconductor (TI) – 800mA fixed and adjustable low dropout linear regulator

ΞϓϦέʔγϣϯɾϊʔτ
1.0 ֎෇͚ίϯσϯα / ҆ఆ౓
1.1 ೖྗόΠύεɾίϯσϯα
ೖྗίϯσϯαͷ࢖༻Λਪ঑͠·͢ɻ 10ЖF ͷλϯλϧɾίϯσϯ
αΛೖྗଆʹऔΓ෇͚Δͱɺ΄΅͢΂ͯͷΞϓϦέʔγϣϯͰద੾
ͳೖྗόΠύε͕ߦ͑·͢ɻ
1.2 ADJ ୺ࢠͷόΠύεɾίϯσϯα
όΠύεɾίϯσϯα (C_ADJ) Λ࢖ͬͯ ADJ ୺ࢠΛάϥ΢ϯυ΁ό
Πύε͢ΔͱɺϦοϓϧআ͢·্͠޲͕཰ڈɻ͜ͷόΠύεɾίϯ
σϯα͸ɺग़ྗిѹ্͕ঢ͢Δʹ࿈ΕͯϦοϓϧ͕૿෯͞ΕΔͷ
Λ๷͗·͢ɻϦοϓϧͷ૿෯Λ๷͙ͨΊʹ͸ɺ͢΂ͯͷϦοϓϧप
೾਺ͰɺC_ADJ ͷΠϯϐʔμϯε͕ R1 ΑΓ΋௿͍ඞཁ͕͋Γ·͢ɻ
1/(2К*f_RIPPLE*C_ADJ) ʻ R1
R1 ͸ɺग़ྗͱ ADJ ୺ࢠͷؒʹ઀ଓͨ͠఍߅Ͱ͢ɻͦͷ஋͸ɺ
௨ৗ 100Њ ʙ 200Њ ͷؒͰ͢ɻͨͱ͑͹ɺR1 ʹ 124Њ Ͱ
f_RIPPLE=120Hz ͷͱ͖ɺC_ADJ ͸ 11ЖF ΑΓେ͖͘ͳΓ·͢ɻ
1.3 ग़ྗίϯσϯα
ग़ྗίϯσϯα͸ɺϨΪϡϨʔλͷ҆ఆ౓Λҡ࣋͢Δ͏͑ͰॏཁͰ
͋Γɺ༰ྔͱ ESR( ౳Ձ௚ྻ఍߅ ) ͷ྆ํ͕ਪ঑஋Λຬͨͯ͠
͍ͳ͚Ε͹ͳΓ·ͤΜɻL1087 ʹඞཁͳ࠷খग़ྗ༰ྔ͸ɺλϯλ
ϧɾίϯσϯαΛ࢖༻͢Δ৔߹ 10ЖF Ͱ͢ɻग़ྗίϯσϯαͷ༰
ྔΛ͜ΕҎ্େ͖ͯ͘͠΋ɺϧʔϓ҆ఆ౓ͱτϥϯδΣϯτԠ౴͕վ
ળ͞ΕΔ͚ͩͰ͢ɻ ग़ྗίϯσϯαͷ ESR ͸ɺ0.5ЊΑΓେ͖͘ɺ
·ͨ 5Њ ະຬͰͳ͚Ε͹ͳΓ·ͤΜɻ ՄมϨΪϡϨʔλͷ৔߹ɺ
C_ADJ Λ࢖༻͢ΔͷͰ͋Ε͹ɺग़ྗίϯσϯαͷ༰ྔΛ૿΍͢ඞ
ཁ͕͋Γ·͢ (22ЖF ͷλϯλϧ )ɻ
2.0 ग़ྗిѹ
L1087ͷՄมిѹόʔδϣϯͰ͸ɺग़ྗͱADJ ୺ࢠͷؒʹ 1.25V
ͷج४ిѹ V_REF Λൃੜ͠·͢ɻFigure 1 ʹࣔ͢ͱ͓Γɺ͜ͷి
ѹ͸఍߅ R1 ʹҹՃ͞ΕͯҰఆͷిྲྀ I1 Λੜ੒͠·͢ɻADJ ୺
ࢠ͔Βͷిྲྀ I_ADJ ͸ɺग़ྗʹࠩޡΛ΋ͨΒ͠·͢ɻ͔͠͠ɺ͜ͷ
ిྲྀ͸ I1 ʹൺ΂ͯඇৗʹখ͘͞(60ЖA)ɺϥΠϯ΍ෛՙ͕มಈ͠
ͯ΋΄΅ҰఆʹอͨΕ͍ͯΔͷͰɺ͜ͷࠩޡ͸ແࢹͰ͖·͢ɻ͜
ͷఆిྲྀ I1 ͸ग़ྗઃఆ఍߅ R2 ΛྲྀΕɺग़ྗిѹ͕ر๬͢Δ
஋ʹઃఆ͞Ε·͢ɻ
ݻఆిѹόʔδϣϯͰ͸ɺR1ͱ R2 ͸σόΠε಺ʹ૊Έࠐ·Εͯ
͍·͢ɻ
ݻఆग़ ྗϨΪϡϨʔλΛ࢖ ༻ͨ͠୅ ද తΞϓϦέʔγϣϯΛɺ
Figure 2 ʹࣔ͠·͢ɻ Rt1ͱ Rt2 ͸഑ઢͷ఍߅෼Ͱ͢ɻ ഑ઢͷ
఍߅ʹΑΔిѹ߱Լ͕͋ΔͨΊɺV_LOAD ͕ V_OUT ΑΓ΋௿͘ͳΔ
͜ͱ͸໌Β͔Ͱ͢ɻ͜ͷ৔߹ɺR_LOAD Ͱଌఆ͞ΕΔϩʔυɾϨΪϡ
Ϩʔγϣϯ͸ɺσʔλγʔτͷ֨نΑΓ΋ѱԽ͠·͢ɻ͜ΕΛվળ͢
ΔͨΊɺෛՙͷਖ਼ଆ͸ग़ྗ୺ࢠ΁௚઀઀ଓ͠ɺෛଆ͸άϥ΢ϯ
υ୺ࢠ΁௚઀઀ଓ͠·͢ɻ
FIGURE 2. Typical Application using Fixed Output
Regulator
ՄมిѹϨΪϡϨʔλΛ࢖༻͢Δ৔߹ (Figure 3) ͸ɺ఍߅ R1 ͷ
ਖ਼ଆΛෛՙʹ͍ۙ఺Ͱ͸ͳ͘ɺϨΪϡϨʔλͷग़ྗ୺ࢠʹ௚઀઀
ଓ͢Δͱɺ࠷ߴͷੑೳ͕ಘΒΕ·͢ɻ͜ͷΑ͏ʹ͢Δͱɺج४ి
ѹͱ௚ྻʹൃੜ͢Δ഑ઢͷిѹ߱ԼͱɺͦΕʹΑΔϨΪϡϨʔγϣ
ϯͷѱ ԽΛ๷ ࢭͰ͖·͢ɻ ͨͱ͑͹ɺϨΪϡϨʔλͱෛՙͷؒʹ
0.05Њ ͷ఍߅෼ͷ͋Δ 5V ϨΪϡϨʔλͰ͸ɺϩʔυɾϨΪϡϨʔ
γϣϯ͸ɺ഑ઢͷ఍߅෼ʹΑͬͯ 0.05Њ ʷ I_L ʹͳΓ·͢ɻ͜ͷͱ
͖ɺR1( ʹ 125Њ) Λෛՙͷۙ͘ʹ઀ଓ͢Δͱɺ࣮ޮ഑ઢ఍߅͸
0.05Њ(1 ʴ R2/R1)ɺ͢ͳΘͪ͜ͷ৔߹͸ 4 ഒ΋ѱԽ͢Δ͜ͱʹͳ
Γ·͢ɻ·ͨɺάϥ΢ϯυଆͷ఍߅ R2 ͕ෛՙͷάϥ΢ϯυͷۙ͘Ͱ
ϦλʔϯΛड͚ΔΑ͏ʹ͢ΔͱɺϦϞʔτɾάϥ΢ϯυݕग़͕ߦΘΕͯ
ϩʔυɾϨΪϡϨʔγϣϯ͕޲্͠·͢ɻ
FIGURE 3. Best Load Regulation using Adjustable
Output Regulator
FIGURE 1. Basic Adjustable Regulator
3.0 ϩʔυɾϨΪϡϨʔγϣϯ
L1087 ͸ɺग़ྗ୺ࢠͱάϥ΢ϯυ୺ࢠؒɺ΋͘͠͸ग़ྗ୺ࢠͱ ADJ
ݱʹؒࢠ୺ΕΔిѹΛ҆ఆԽ͠·͢ɻ͔͠͠ɺ഑ઢͷ఍߅ʹ͔
͔ΔෛՙʹΑΔిѹ߱ԼʹΑ͕ͬͯࠩޡੜ͡Δ͜ͱ͕͋Γ·͢ɻ
ϩʔυɾϨΪϡϨʔγϣϯΛ࠷ྑͷঢ়ଶʹอͭͨΊʹ͸ɺ஫ҙ͢΂
͖఺͕͍͔ͭ͋͘Γ·͢ɻ
4.0 อޢμΠΦʔυ
௨ৗͷಈ࡞தɺL1087 ϨΪϡϨʔλ͸อޢμΠΦʔυΛඞཁͱ͠·
ͤΜɻՄมిѹόʔδϣϯͰ͸ɺADJ ୺ࢠͱग़ྗ୺ࢠؒͷ಺ଂ
఍߅ʹΑͬͯిྲ੍ྀ͕͞ݶΕ·͢ɻADJ ୺ࢠʹίϯσϯαΛ઀ଓ
͍ͯ͠Δ৔߹Ͱ͋ͬͯ΋ɺϨΪϡϨʔλपลͷిྲྀΛӌճͤ͞Δμ
ΠΦʔυ͸ෆཁͰ͢ɻ ADJ ୺ࢠ͸ɺຊσόΠεΛଛই͢Δ͜ͱͳ
͘ɺग़ྗిѹΛج४ʹͯ͠ʶ 25V ͷτϥϯδΣϯτ৴߸Λड͚ೖΕ
Δ͜ͱ͕Ͱ͖·͢ɻ
3
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