ZHCSB50K December 2012 – May 2019 TPS50301-HT
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 VIN and Power VIN Pins (VIN and PVIN)
- 8.3.2 PVIN vs Frequency
- 8.3.3 Voltage Reference
- 8.3.4 Adjusting the Output Voltage
- 8.3.5 Maximum Duty Cycle Limit
- 8.3.6 PVIN vs Frequency
- 8.3.7 Safe Start-Up into Prebiased Outputs
- 8.3.8 Error Amplifier
- 8.3.9 Slope Compensation
- 8.3.10 Enable and Adjust UVLO
- 8.3.11 Adjustable Switching Frequency and Synchronization (SYNC)
- 8.3.12 Slow Start (SS/TR)
- 8.3.13 Power Good (PWRGD)
- 8.3.14 Bootstrap Voltage (BOOT) and Low Dropout Operation
- 8.3.15 Sequencing (SS/TR)
- 8.3.16 Output Overvoltage Protection (OVP)
- 8.3.17 Overcurrent Protection
- 8.3.18 TPS50301-HT Thermal Shutdown
- 8.3.19 Turn-On Behavior
- 8.3.20 Small Signal Model for Loop Response
- 8.3.21 Simple Small Signal Model for Peak Current Mode Control
- 8.3.22 Small Signal Model for Frequency Compensation
- 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 Custom Design With WEBENCH® Tools
- 9.2.2.2 Operating Frequency
- 9.2.2.3 Output Inductor Selection
- 9.2.2.4 Output Capacitor Selection
- 9.2.2.5 Input Capacitor Selection
- 9.2.2.6 Slow Start Capacitor Selection
- 9.2.2.7 Bootstrap Capacitor Selection
- 9.2.2.8 Undervoltage Lockout (UVLO) Set Point
- 9.2.2.9 Output Voltage Feedback Resistor Selection
- 9.2.2.10 Compensation Component Selection
- 9.2.3 Parallel Operation
- 9.2.4 Application Curve
- 10Power Supply Recommendations
- 11Layout
- 12器件和文档支持
- 13机械、封装和可订购信息
9.2.2.3 Output Inductor Selection
To calculate the value of the output inductor, use Equation 20. KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current. The inductor ripple current is filtered by the output capacitor. Therefore, choosing high inductor ripple currents impact the selection of the output capacitor since the output capacitor must have a ripple current rating equal to or greater than the inductor ripple current. In general, the inductor ripple value (Iout x Kind) is at the discretion of the designer.
For this design example, use KIND = 0.3 and the inductor value is calculated to be 2.7 µH. For this design, a nearest standard value was chosen: 3.3 µH. For the output filter inductor, it is important that the RMS current and saturation current ratings not be exceeded. The RMS and peak inductor current can be found from Equation 22 and Equation 23.
For this design, the RMS inductor current is 3.01 A and the peak inductor current is 3.49 A. The chosen inductor is a Coilcraft MSS1048 series 3.3 µH. It has a saturation current rating of 7.38 A and a RMS current rating of 7.22 A.
The current flowing through the inductor is the inductor ripple current plus the output current. During power up, faults or transient load conditions, the inductor current can increase above the calculated peak inductor current level calculated above. In transient conditions, the inductor current can increase up to the switch current limit of the device. For this reason, the most conservative approach is to specify an inductor with a saturation current rating equal to or greater than the switch current limit rather than the peak inductor current.