V-CHIP ALUMINUM ELECTROLYTIC CAPACITORS 䊐⠛ᓣ䢕䳏㾷䳏ᆍ఼ LIFE OF ALUMINUM ELECTROLYTIC CAPACITORS 䊐⠛ᓣ䢕䳏㾷䳏ᆍ఼ The life of aluminum electrolytic capacitors is mainly dependent on environmental conditions (e.g. ambient temperature, humidity etc.) and electrical factors (e.g. operating temperature, ripple current etc.). Generally, the wear-out mechanism of aluminum electrolytic capacitors is based on evaporation of electrolyte through the rubber seal. Consequently, the factor of temperature (ambient temperature and internal heating due to ripple current) is the most critical to electrolytic capacitors life. The effect of voltage on capacitor life is negligible, especially for low voltage electrolytic capacitors. The lifetime of aluminum electrolytic capacitors can be expressed as following equations. 䢕䳏㾷䳏ᆍ఼ⱘ໑ੑЏ㽕ձ䋈ᮐ݊䘽⫼ⱘ⪄๗ṱӊ˄བ⑿ᑺǃ▩ᑺㄝ˅䳏䉴㥋ᚙ⊕˄བᎹ䳏ວǃ㋟⊶䳏⌕ㄝ˅ DŽ䗮ᐌ㗠㿔ˈ 䢕䳏㾷䳏ᆍ఼ⱘ༅ᬜ″⧚㹿䁡⠆ᰃ䳏㾷⎆䗮䘢㝴า䗤┌ᧂⱐ᠔ᇢ㟈DŽℸˈ⑿ᑺ㋴˄⪄๗⑿ᑺ⬅ᮐ㋟⊶䳏⌕᠔ᓩ㟈ⱘܻ➅˅ ᇡ䳏ᆍ఼໑ੑⱘᕅ䷓᳔ˈ㗠䳏ວᇡ䳏ᆍ఼໑ੑⱘᕅ䷓ৃҹᗑ⬹ˈᇸ݊ᇡԢ䳏ວ䢕䳏㾷䳏ᆍ఼ᰃབℸDŽ䢕䳏㾷䳏ᆍ఼ⱘ໑ੑ ৃ⫼ϟ߫݀ᓣ՚Ԅㅫ˖ Le=LogKtgKr Where: ݊Ё: Le=Expected life at operating temperature Te(h) Ꮉ⑿ᑺ Te(h)ϟⱘ䷤ᳳ໑ੑ Lo=Specified life at maximum operating temperature To(h) ᳔Ꮉ⑿ᑺ To(h)ϟⱘ໑ੑ Kt=Ambient temperature acceleration term ⪄๗⑿ᑺᕅ䷓ᄤ Kr=Ripple current acceleration term ㋟⊶䳏⌕ᕅ䷓ᄤ (ToˉTe)/10 H C Kt=LogA Where: ݊Ё: To=Maximum rated operating temperature(ć) ᳔両ᅮᎹ䳏ວ⑿ᑺ˄ć˅ Te=Actual ambient temperature(ć) ᆺ䱯⪄๗䘽⫼⑿ᑺ˄ć˅ A=Acceleration coefficient (for the range from 35ć to the maximum operating temperature, AĬ2) ࡴ䗳֖ᭌ˄ᇡᮐᕲ 35ćࠄ᳔催Ꮉ⑿ᑺⱘ㆘ೡˈAĬ2˅ E T Kr=2(ˉƸT/5) Where: ݊Ё: ƸT=An increase in core temperature by internal heating due to ripple current ⬅ᮐ㋟⊶䳏⌕ᓩ䍋ⱘܻ➅䗴៤䳏ᆍ఼㢃ᄤⱘछ⑿ ˄ƸT=core temperatureˉambient temperature˅ ˄ƸT=㢃ᄤ⑿ᑺˉ⪄๗⑿ᑺ˅ M E ƸT can be estimated as follows: ƸT ৃ⫼ҹϟ݀ᓣԄㅫ˖ ƸT=(I2gR)/( £gS) Where: ݊Ё: I=Ripple current of the capacitor (A rms) 䗮䘢䳏ᆍ఼ⱘ㋟⊶䳏⌕˄A rms˅ R=Equivalent series resistance of the capacitor (¡) 䳏ᆍ఼ⱘㄝᬜІ㙃䳏䰏˄¡˅ ȕ=Heat radiation coefficient of the aluminum can (W/ćgcm2) 䢕←ⱘ➅䔏ᇘ֖ᭌ˄W/ćgcm2˅ S=Surface area of the capacitor (cm2) 䳏ᆍ఼ⱘ㸼䴶〡˄cm2˅ S Quick Reference Guide of the Expected Life ䷤ᳳ໑ੑᖿ䗳গ㗗 NOTE: All designs and specifications are for reference only and are subject to change without prior notice. If any doubt about safety for your application, please contact us immediately for technical assistance before purchase. ⊼: ҹϞ᠔ᦤկⱘ䀁㿜ঞ⡍ᗻগᭌڙկগ㗗⫼ˈӏԩׂᬍϡ䷤ܜ䗮ⶹDŽབᵰՓ⫼Ϟ᳝⭥ଣˈ䂟䞛䋐ࠡ㟛៥ץ㙃㌵ˈҹ֓ᦤկᡔ㸧ϞⱘनࡽDŽ SEMTECH ELECTRONICS LTD. (Subsidiary of Sino-Tech International Holdings Limited, a company listed on the Hong Kong Stock Exchange, Stock Code: 724) ® 15