ZHCSHO2G June 2010 – February 2018 TPS65251
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 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 Adjustable Switching Frequency
- 8.3.2 Synchronization
- 8.3.3 Out-of-Phase Operation
- 8.3.4 Delayed Start-Up
- 8.3.5 Soft-Start Time
- 8.3.6 Adjusting the Output Voltage
- 8.3.7 Input Capacitor
- 8.3.8 Bootstrap Capacitor
- 8.3.9 Error Amplifier
- 8.3.10 Loop Compensation
- 8.3.11 Slope Compensation
- 8.3.12 Powergood
- 8.3.13 Current Limit Protection
- 8.3.14 Overvoltage Transient Protection
- 8.3.15 Thermal Shutdown
- 8.4 Device Functional Modes
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Application
- 9.2.1 Design Requirements
- 9.2.2
Detailed Design Procedure
- 9.2.2.1 Loop Compensation Circuit
- 9.2.2.2 Selecting the Switching Frequency
- 9.2.2.3 Output Inductor Selection
- 9.2.2.4 Output Capacitor
- 9.2.2.5 Input Capacitor
- 9.2.2.6 Soft-Start Capacitor
- 9.2.2.7 Bootstrap Capacitor Selection
- 9.2.2.8 Adjustable Current Limiting Resistor Selection
- 9.2.2.9 Output Voltage and Feedback Resistors Selection
- 9.2.2.10 Compensation
- 9.2.2.11 3.3-V and 6.5-V LDO Regulators
- 9.2.3 Application Curves
- 10Power Supply Recommendations
- 11Layout
- 12器件和文档支持
- 13机械、封装和可订购信息
9.2.2.6 Soft-Start Capacitor
The soft-start capacitor determines the minimum amount of time it will take for the output voltage to reach its nominal programmed value during power-up. This is useful if the output capacitance is very large and would require large amounts of current to quickly charge the capacitor to the output voltage level.
The soft-start capacitor value can be calculated using Equation 24. In this example, the converter’s soft-start time is 0.8 ms. In TPS65251, Iss is 5 µA and Vref is 0.8 V. From Equation 24, the soft-start capacitance is 5 nF. A standard 4.7-nF ceramic capacitor is chosen in this design. In this example, C16 is 4.7nF
Equation 24. 