Datasheet TPS54332 (Texas Instruments) - 9
| Manufacturer | Texas Instruments |
| Description | 3.5-A, 28-V, 1-MHz, Step-Down DC-DC Converter With Eco-Mode |
| Pages / Page | 34 / 9 — TPS54332. www.ti.com. 7 Detailed Description. 7.1 Overview |
| Revision | C |
| File Format / Size | PDF / 1.5 Mb |
| Document Language | English |
TPS54332. www.ti.com. 7 Detailed Description. 7.1 Overview
Model Line for this Datasheet
TPS54332
Text Version of Document
TPS54332 www.ti.com
SLVS875C – JANUARY 2009 – REVISED NOVEMBER 2014
7 Detailed Description 7.1 Overview
The TPS54332 is a 28-V, 3.5-A, step-down (buck) converter with an integrated high-side, N-channel MOSFET. To improve performance during line and load transients, the device implements a constant-frequency, current mode control, which reduces output capacitance and simplifies external frequency compensation design. The TPS54332 has a pre-set switching frequency of 1 MHz. The TPS54332 needs a minimum input voltage of 3.5 V to operate normally. The EN pin has an internal pullup current source that can be used to adjust the input voltage undervoltage lockout (UVLO) with two external resistors. In addition, the pullup current provides a default condition when the EN pin is floating for the device to operate. The operating current is 82 μA typically when not switching and under no load. When the device is disabled, the supply current is 1 μA typically. The integrated 80-mΩ high-side MOSFET allows for high-efficiency power supply designs with continuous output currents up to 3.5 A. The TPS54332 reduces the external component count by integrating the boot recharge diode. The bias voltage for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pin. The boot capacitor voltage is monitored by an UVLO circuit and will turn the high-side MOSFET off when the voltage falls below a preset threshold of 2.1 V typically. The output voltage can be stepped down to as low as the reference voltage. By adding an external capacitor, the slow-start time of the TPS54332 can be adjustable which enables flexible output filter selection. To improve the efficiency at light load conditions, the TPS54332 enters a special pulse-skipping Eco-Mode when the peak inductor current drops below 160 mA typically. The frequency foldback reduces the switching frequency during start-up and over current conditions to help control the inductor current. The thermal shutdown gives the additional protection under fault conditions. Copyright © 2009–2014, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: TPS54332 Document Outline 1 Features 2 Applications 3 Description Table of Contents 4 Revision History 5 Pin Configuration and Functions 6 Specifications 6.1 Absolute Maximum Ratings 6.2 Handling Ratings 6.3 Recommended Operating Conditions 6.4 Thermal Information 6.5 Electrical Characteristics 6.6 Switching Characteristics 6.7 Typical Characteristics: Characterization Curves 6.8 Typical Characteristics: Supplemental Application Curves 7 Detailed Description 7.1 Overview 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Fixed Frequency PWM Control 7.3.2 Voltage Reference (Vref) 7.3.3 Bootstrap Voltage (BOOT) 7.3.4 Enable and Adjustable Input Undervoltage Lockout (VIN UVLO) 7.3.5 Programmable Slow-Start Using SS Pin 7.3.6 Error Amplifier 7.3.7 Slope Compensation 7.3.8 Current Mode Compensation Design 7.3.9 Overcurrent Protection and Frequency Shift 7.3.10 Overvoltage Transient Protection 7.3.11 Thermal Shutdown 7.4 Device Functional Modes 7.4.1 Operation With VIN < 3.5 V 7.4.2 Operation With EN Control 7.4.3 Eco-Mode 8 Application and Implementation 8.1 Application Information 8.2 Typical Application 8.2.1 Design Requirements 8.2.2 Detailed Design Procedure 8.2.2.1 Switching Frequency 8.2.2.2 Output Voltage Set Point 8.2.2.3 Input Capacitors 8.2.2.4 Output Filter Components 8.2.2.5 Inductor Selection 8.2.2.6 Capacitor Selection 8.2.2.7 Compensation Components 8.2.2.8 Bootstrap Capacitor 8.2.2.9 Catch Diode 8.2.2.10 Output Voltage Limitations 8.2.2.11 Power Dissipation Estimate 8.2.3 Application Curves 9 Power Supply Recommendations 10 Layout 10.1 Layout Guidelines 10.2 Layout Example 10.3 Estimated Circuit Area 10.4 Electromagnetic Interference (EMI) Considerations 11 Device and Documentation Support 11.1 Device Support 11.1.1 Development Support 11.2 Trademarks 11.3 Electrostatic Discharge Caution 11.4 Glossary 12 Mechanical, Packaging, and Orderable Information
SLVS875C – JANUARY 2009 – REVISED NOVEMBER 2014
7 Detailed Description 7.1 Overview
The TPS54332 is a 28-V, 3.5-A, step-down (buck) converter with an integrated high-side, N-channel MOSFET. To improve performance during line and load transients, the device implements a constant-frequency, current mode control, which reduces output capacitance and simplifies external frequency compensation design. The TPS54332 has a pre-set switching frequency of 1 MHz. The TPS54332 needs a minimum input voltage of 3.5 V to operate normally. The EN pin has an internal pullup current source that can be used to adjust the input voltage undervoltage lockout (UVLO) with two external resistors. In addition, the pullup current provides a default condition when the EN pin is floating for the device to operate. The operating current is 82 μA typically when not switching and under no load. When the device is disabled, the supply current is 1 μA typically. The integrated 80-mΩ high-side MOSFET allows for high-efficiency power supply designs with continuous output currents up to 3.5 A. The TPS54332 reduces the external component count by integrating the boot recharge diode. The bias voltage for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pin. The boot capacitor voltage is monitored by an UVLO circuit and will turn the high-side MOSFET off when the voltage falls below a preset threshold of 2.1 V typically. The output voltage can be stepped down to as low as the reference voltage. By adding an external capacitor, the slow-start time of the TPS54332 can be adjustable which enables flexible output filter selection. To improve the efficiency at light load conditions, the TPS54332 enters a special pulse-skipping Eco-Mode when the peak inductor current drops below 160 mA typically. The frequency foldback reduces the switching frequency during start-up and over current conditions to help control the inductor current. The thermal shutdown gives the additional protection under fault conditions. Copyright © 2009–2014, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: TPS54332 Document Outline 1 Features 2 Applications 3 Description Table of Contents 4 Revision History 5 Pin Configuration and Functions 6 Specifications 6.1 Absolute Maximum Ratings 6.2 Handling Ratings 6.3 Recommended Operating Conditions 6.4 Thermal Information 6.5 Electrical Characteristics 6.6 Switching Characteristics 6.7 Typical Characteristics: Characterization Curves 6.8 Typical Characteristics: Supplemental Application Curves 7 Detailed Description 7.1 Overview 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Fixed Frequency PWM Control 7.3.2 Voltage Reference (Vref) 7.3.3 Bootstrap Voltage (BOOT) 7.3.4 Enable and Adjustable Input Undervoltage Lockout (VIN UVLO) 7.3.5 Programmable Slow-Start Using SS Pin 7.3.6 Error Amplifier 7.3.7 Slope Compensation 7.3.8 Current Mode Compensation Design 7.3.9 Overcurrent Protection and Frequency Shift 7.3.10 Overvoltage Transient Protection 7.3.11 Thermal Shutdown 7.4 Device Functional Modes 7.4.1 Operation With VIN < 3.5 V 7.4.2 Operation With EN Control 7.4.3 Eco-Mode 8 Application and Implementation 8.1 Application Information 8.2 Typical Application 8.2.1 Design Requirements 8.2.2 Detailed Design Procedure 8.2.2.1 Switching Frequency 8.2.2.2 Output Voltage Set Point 8.2.2.3 Input Capacitors 8.2.2.4 Output Filter Components 8.2.2.5 Inductor Selection 8.2.2.6 Capacitor Selection 8.2.2.7 Compensation Components 8.2.2.8 Bootstrap Capacitor 8.2.2.9 Catch Diode 8.2.2.10 Output Voltage Limitations 8.2.2.11 Power Dissipation Estimate 8.2.3 Application Curves 9 Power Supply Recommendations 10 Layout 10.1 Layout Guidelines 10.2 Layout Example 10.3 Estimated Circuit Area 10.4 Electromagnetic Interference (EMI) Considerations 11 Device and Documentation Support 11.1 Device Support 11.1.1 Development Support 11.2 Trademarks 11.3 Electrostatic Discharge Caution 11.4 Glossary 12 Mechanical, Packaging, and Orderable Information
