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Texas Instruments TPS40003 manual Compensation Design, 2 p, p R, R4 R5

Models: TPS40003

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SLUU130A – September 2002 – Revised February 2003

4.7Compensation Design

The TPS40003 uses voltage mode control in conjunction with a high frequency error amplifier. For the fastest transient response, the loop crossover frequency is set at 1/10 fS, or 60 kHz. The power circuit L-C double pole corner frequency fC is situated at 24 kHz, and the output capacitor ESR zero is far higher at approximately 1MHz. The feedback compensation network is implemented to provide two zeroes and three poles. The first pole is placed at the origin to improve dc regulation.

The first zero is placed at approximately 2/3 fC, 18 kHz,

fz1

(6)

The second zero is selected at fC,

fz2

(7)

2 p

R4 ) R5

C12

The two poles are placed at approximately 300 kHz, which is one-half the switching frequency,

fp1 +

(8)

2 p R2

C4)C8

and

fp2

(9)

C12

8TPS40003-Based 5-A Converter in Less Than One Square Inch

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Texas Instruments TPS40003 manual Compensation Design, 2 p, p R, R4 R5

Contents

User’s Guide User’s GuideTPS40003 Based 5-A Converter in Less Than One Square Inch EVM IMPORTANT NOTICE DYNAMIC WARNINGS AND RESTRICTIONS 2 Features 1 IntroductionContents 1 Introduction 2 Features 3 Schematic 4 Design Procedure 5 PowerPAD Packaging 6 Test Results/Performance Data 7 PCB Layout3 Schematic Figure 1. Application Diagram for the TPS40002/3SLUU130A - September 2002 - Revised February TPS40003-Based 5-A Converter in Less Than One Square Inch4 Design Procedure 4.1 TPS4000X Family Device Selection4.2 Inductance Value 4.3 Input Capacitor Selection4.6 Short Circuit Protection 4.4 Output Capacitor Selection4.5 MOSFET Selection 4.7 Compensation Design 2 p2 p R R4 R54.8 Snubber Component Selection 100005 PowerPAD Packaging Figure 3. PowerPAD PCB Layout Guidelines6 Test Results/Performance Data The test setup is shown in figureSLUU130A - September 2002 - Revised February TPS40003-Based 5-A Converter in Less Than One Square InchTypical efficiency curves are shown in Figure 5 for an input of 3.3 SHORT CIRCUIT OPERATION 2 V/div t - Time - 1 ms/div OUTPUT VOLTAGE RIPPLE 10 mV/div t - Time - 500 ns/divSTARTUP WAVEFORM 1 V/div 500 mV/div 500 mV/div t - Time - 200 ∝ s/div TRANSIENT RESPONSE 50 mV/div t - Time - 20 ∝ s/divTPS40003-Based 5-A Converter in Less Than One Square Inch 7 PCB LayoutSLUU130A - September 2002 - Revised February 8 List of Material SLUU130A - September 2002 - Revised February16 TPS40003-Based 5-A Converter in Less Than One Square Inch ReferenceIMPORTANT NOTICE

4.7Compensation Design

2 p

￿R4 ) R5￿

2 p R2 ￿

R4 ) R5

2 p R2