04-LDO - Low Drop-Out (LDO) Regulator Chern-Lin Chen ( )...

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Chern-Lin Chen ( ) Department of Electrical Engineering & Graduate Institute of Electronics Engineering National Taiwan University e-mail - clchen@cc.ee.ntu.edu.tw office tel – +886-2-3366-3575 Low Drop-Out (LDO) Regulator Mar. 16, 2010
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1 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 Linear Regulator Series regulator Shunt regulator pass element feedback control load Vout Vout shunt element feedback control load
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2 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 Basics of Series Linear Regulator REF OUT V R R V × + = ) / 1 ( 2 1 () in out VV + −− R 1 R 2 regulation quiescent current operating voltage 12 (1 / ) REF out VR R V =+ ×
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3 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 Features (compared with switching power) Advantages Fast response Simple circuit Low cost Low noise Low V out ripple Drawbacks Low efficiency Depend on (V in -V out ) and quiescent current Step down only One output only
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4 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 NMOS Pass Element •N M O S –L o w e r R ON – No gate current – Difficult to drive (better with one >Vin source) V GS
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5 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 PMOS Pass Element •P M O S –V dropout =I O R ON 35~350mV – No gate current
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6 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 System Design Issues DC characteristics Efficiency Dropout voltage Load regulation Line regulation Transient response Voltage variation due to load current steps Power supply rejection ratio Frequency domain analysis Stability
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7 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 Efficiency Limited by I q and V out /Vin •( V in -V out ) and I q should be minimized () oo u t oqi n IV Efficiency = 100% I+ I V × Iq : quiescent current
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8 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 Dropout Voltage • Dropout voltage V dropout V in,min = V out +V dropout V in V in V out
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9 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 Operations of Pass Element Saturation region voltage controlled current source Triode region resistor R ON (V SD =I OUT R ON ) V SD I SD V SG1 V SG2 V SG3 I LOAD1 I LOAD2
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10 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 National Taiwan University 國立台灣大學 In Saturation ?
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04-LDO - Low Drop-Out (LDO) Regulator Chern-Lin Chen ( )...

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