ZHCS984B June 2012 – May 2019 TPS54678
PRODUCTION DATA.
- 1 特性
- 2 應用
- 3 說明
- 4 修訂歷史記錄
- 5 Pin Configuration and Functions
- 6 Specifications
-
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 Slope Compensation and Output Current
- 7.3.3 Bootstrap Voltage (Boot) and Low Dropout Operation
- 7.3.4 Error Amplifier
- 7.3.5 Voltage Reference
- 7.3.6 Adjusting the Output Voltage
- 7.3.7 Enable and Adjusting Undervoltage Lockout
- 7.3.8 Soft-Start Pin
- 7.3.9 Sequencing
- 7.3.10 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
- 7.3.11 Overcurrent Protection
- 7.3.12 Safe Start-Up into Prebiased Outputs
- 7.3.13 Synchronize Using the RT/CLK Pin
- 7.3.14 Power Good (PWRGD Pin)
- 7.3.15 Overvoltage Transient Protection
- 7.3.16 Thermal Shutdown
- 7.4 Device Functional Modes
-
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 Custom Design With WEBENCH® Tools
- 8.2.2.2 Step One: Select the Switching Frequency
- 8.2.2.3 Step Two: Select the Output Inductor
- 8.2.2.4 Step Three: Choose the Output Capacitor
- 8.2.2.5 Step Four: Select the Input Capacitor
- 8.2.2.6 Step Five: Choose the Soft-Start Capacitor
- 8.2.2.7 Step Six: Select the Bootstrap Capacitor
- 8.2.2.8 Step Eight: Select Output Voltage and Feedback Resistors
- 8.2.2.9 Step Nine: Select Loop Compensation Components
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文檔支持
- 12機械、封裝和可訂購信息
8.2.2.2 Step One: Select the Switching Frequency
The first step is to decide on a switching frequency for the regulator. Typically, it is desirable to choose the highest switching frequency possible since this produces the smallest component solution size. The high switching frequency allows for lower value inductors and smaller output capacitors compared to a power supply that switches at a lower frequency. However, the higher switching frequency causes extra switching losses, which degrade the performance of the converter. This SWIFT™ converter is capable of running from 200 kHz to
2 MHz. Unless a small solution size is the top priority, a moderate switching frequency of 500 kHz is selected to achieve both a small solution size and high-efficiency operation. Using Equation 13, RT is calculated to be
81.34 kΩ. A standard 1% 82.5-kΩ value was chosen for the design.
where
- RT is in kΩ
- FSW is in kHz