ZHCSCL9A July 2014 – September 2021 TPS55340-EP
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 说明（续）
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Switching Frequency
- 8.3.2 Voltage Reference and Setting Output Voltage
- 8.3.3 Soft Start
- 8.3.4 Slope Compensation
- 8.3.5 Overcurrent Protection and Frequency Foldback
- 8.3.6 Enable and Thermal Shutdown
- 8.3.7 Undervoltage Lockout (UVLO)
- 8.3.8 Minimum On-Time and Pulse Skipping
- 8.3.9 Layout Considerations
- 8.3.10 Thermal Considerations
- 8.4 Device Functional Modes
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Applications
- 9.2.1
Boost Converter Application
- 9.2.1.1 Design Requirements
- 9.2.1.2
Detailed Design Procedure
- 9.2.1.2.1 Selecting the Switching Frequency (R4)
- 9.2.1.2.2 Determining the Duty Cycle
- 9.2.1.2.3 Selecting the Inductor (L1)
- 9.2.1.2.4 Computing the Maximum Output Current
- 9.2.1.2.5 Selecting the Output Capacitor (C8 to C10)
- 9.2.1.2.6 Selecting the Input Capacitors (C2, C7)
- 9.2.1.2.7 Setting Output Voltage (R1, R2)
- 9.2.1.2.8 Setting the Soft-Start Time (C7)
- 9.2.1.2.9 Selecting the Schottky Diode (D1)
- 9.2.1.2.10 Compensating the Control Loop (R3, C4, C5)
- 9.2.1.3 Application Curves
- 9.2.2
SEPIC Converter Application
- 9.2.2.1 Design Requirements
- 9.2.2.2
Detailed Design Procedure
- 9.2.2.2.1 Selecting the Switching Frequency (R4)
- 9.2.2.2.2 Duty Cycle
- 9.2.2.2.3 Selecting the Inductor (L1)
- 9.2.2.2.4 Calculating the Maximum Output Current
- 9.2.2.2.5 Selecting the Output Capacitor (C8 to C10)
- 9.2.2.2.6 Selecting the Series Capacitor (C6)
- 9.2.2.2.7 Selecting the Input Capacitor (C2, C7)
- 9.2.2.2.8 Selecting the Schottky Diode (D1)
- 9.2.2.2.9 Setting the Output Voltage (R1, R2)
- 9.2.2.2.10 Setting the Soft-Start Time (C3)
- 9.2.2.2.11 MOSFET Rating Considerations
- 9.2.2.2.12 Compensating the Control Loop (R3, C4)
- 9.2.2.3 SEPIC Converter Application Curves
- 9.2.1
Boost Converter Application
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
9.2.1.2.4 Computing the Maximum Output Current
The overcurrent limit for the integrated power MOSFET limits the maximum input current and thus the maximum input power for a given input voltage. Maximum output power is less than maximum input power due to power conversion losses. Therefore, the current limit setting, input voltage, output voltage, and efficiency can all change maximum current output (IOUTmax). The current limit clamps the peak inductor current; therefore, the ripple has to be subtracted to derive maximum DC current. Decreasing the KIND or designing for a higher efficiency will increase the maximum output current. This can be evaluated with the chosen inductance or the chosen KIND. This should be evaluated with the minimum input voltage and minimum peak current limit (ILIM) of 5.25 A.
In this design with 5 V input boosted to 24 V output and a 10-μH inductor with an assumed the Schottky forward voltage of 0.5 V and estimated efficiency of 85%, the maximum output current is 871 mA. With the 12-V input and increased estimated efficiency of 90%, the maximum output current increases to 2.13 A. This circuit was evaluated to its maximum output currents with both the minimum and maximum input voltage.