Datasheet ADP1821 (Analog Devices) - 2

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ADP1821 TABLE OF CONTENTS
Features .. 1 Compensation... 11 Applications... 1 Power-Good Indicator... 11 General Description ... 1 Thermal Shutdown .. 11 Revision History ... 2 Shutdown Control.. 11 Specifications... 3 Application Information.. 12 Absolute Maximum Ratings.. 5 Selecting the Input Capacitor ... 12 ESD Caution.. 5 Output LC Filter ... 12 Simplified Block Diagram ... 5 Selecting the MOSFETs ... 13 Pin Configuration and Function Descriptions... 6 Setting the Current Limit .. 14 Typical Performance Characteristics ... 7 Feedback Voltage Divider ... 14 Theory of Operation .. 9 Compensating the Voltage Mode Buck Regulator... 14 Soft Start .. 9 Setting the Soft Start Period.. 18 Error Amplifier ... 9 PCB Layout Guideline ... 19 Current-Limit Scheme... 9 Recommended Component Manufacturers... 20 MOSFET Drivers.. 10 Application Circuits ... 21 Input Voltage Range ... 10 Outline Dimensions ... 23 Setting the Output Voltage .. 10 Ordering Guide .. 23 Switching Frequency Control and Synchronization.. 10
REVISION HISTORY 4/07—Rev. B to Rev. C
Changes to Theory of Operation Section...9 Changes to Application Information Section ... 12 Changes to Specifications Section .. 3 Added PCB Layout Section... 19 Changes to Absolute Maximum Ratings Section ... 5 Changes to Application Circuits Section... 21 Changes to Current-Limit Scheme Section .. 10 Added Summary of Equations Section.. 23 Changes to Setting the Current Limit Section.. 14 Added Figure 15.. 14 Changes to Compensating the Voltage Mode Buck
1/06—Rev. 0 to Rev. A
Regulator Section.. 15 Changes to Specifications Table ..3 Changes to Type II Compensator Section... 17 Changes to Theory of Operation Section.. 10 Changes to Type III Compensator Section ... 18 Changes to Input Voltage Range Section .. 11 Changes to Application Circuits Section... 21 Added Equation 1... 12 Changes to Figure 22.. 21 Changes to Equation 7 and Equation 8 ... 13 Changes to Ordering Guide .. 23 Added Equation 9... 13 Changes to Equation 16... 14
12/06—Rev. A to Rev. B
Changes to Figure 15.. 14 Updated Format..Universal Changes to Equation 21... 15 Changes to Features Section.. 1 Changes to Figure 16.. 15 Changes to Applications Section .. 1 Changes to Equation 28... 15 Changes to General Description Section .. 1 Updated Outline Dimensions... 18 Changes to Error Amplifier... 3
7/05—Revision 0: Initial Version
Changes to PWM Controller .. 3 Changes to Oscillator Frequency.. 3 Rev. C | Page 2 of 24 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION SIMPLIFIED BLOCK DIAGRAM PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION SOFT START ERROR AMPLIFIER CURRENT-LIMIT SCHEME MOSFET DRIVERS INPUT VOLTAGE RANGE SETTING THE OUTPUT VOLTAGE SWITCHING FREQUENCY CONTROL AND SYNCHRONIZATION COMPENSATION POWER-GOOD INDICATOR THERMAL SHUTDOWN SHUTDOWN CONTROL APPLICATION INFORMATION SELECTING THE INPUT CAPACITOR OUTPUT LC FILTER SELECTING THE MOSFETS SETTING THE CURRENT LIMIT FEEDBACK VOLTAGE DIVIDER COMPENSATING THE VOLTAGE MODE BUCK REGULATOR Type II Compensator Type III Compensator SETTING THE SOFT START PERIOD PCB LAYOUT GUIDELINE RECOMMENDED COMPONENT MANUFACTURERS APPLICATION CIRCUITS OUTLINE DIMENSIONS ORDERING GUIDE