ZHCSI26C August 2010 – April 2018 TPS54320
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 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 Continuous Current Mode Operation (CCM)
- 7.3.3 VIN and Power VIN Pins (VIN and PVIN)
- 7.3.4 Voltage Reference
- 7.3.5 Adjusting the Output Voltage
- 7.3.6 Safe Start-up into Prebiased Outputs
- 7.3.7 Error Amplifier
- 7.3.8 Slope Compensation
- 7.3.9 Enable and Adjusting UVLO
- 7.3.10 Slow Start (SS/TR)
- 7.3.11 Power Good (PWRGD)
- 7.3.12 Bootstrap Voltage (BOOT) and Low Dropout Operation
- 7.3.13 Sequencing (SS/TR)
- 7.3.14 Output Overvoltage Protection (OVP)
- 7.3.15 Overcurrent Protection
- 7.3.16 Thermal Shutdown
- 7.3.17 Small Signal Model for Loop Response
- 7.3.18 Simple Small Signal Model for Peak Current Mode Control
- 7.3.19 Small Signal Model for Frequency Compensation
- 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 Operating Frequency
- 8.2.2.3 Output Inductor Selection
- 8.2.2.4 Output Capacitor Selection
- 8.2.2.5 Input Capacitor Selection
- 8.2.2.6 Slow-Start Capacitor Selection
- 8.2.2.7 Bootstrap Capacitor Selection
- 8.2.2.8 UVLO Set Point
- 8.2.2.9 Output Voltage Feedback Resistor Selection
- 8.2.2.10 Compensation Component Selection
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
8.2.2.5 Input Capacitor Selection
The TPS54320 requires a high-quality ceramic, type X5R or X7R, input decoupling capacitor of 4.7 µF on each input voltage rail. In some applications, additional bulk capacitance may also be required for the PVIN input. The voltage rating of the input capacitor must be greater than the maximum input voltage. The capacitor must also have a ripple current rating greater than the maximum input current ripple of the TPS54320. The input ripple current for this design, using Equation 27, is 1.48 A.
The value of a ceramic capacitor varies significantly over both temperature and the amount of DC bias applied to the capacitor. The capacitance variations due to temperature can be minimized by selecting a dielectric material that is stable over temperature. X5R and X7R ceramic dielectrics are usually selected for power regulator capacitors because of the high capacitance to volume ratio and stability over temperature. The capacitance value of a capacitor decreases as the DC bias across it increases. For this example design, a ceramic capacitor with at least a 25-V voltage rating is required to support the maximum input voltage. For this example, two 4.7-µF 25-V capacitors were used in parallel as the VIN and PVIN inputs are tied together, so the TPS54320 may operate from a single supply. The input capacitance value determines the input ripple voltage of the regulator. The input voltage ripple can be calculated using Equation 28. Using the design example values, Ioutmax = 3 A, CIN = 9.4 μF, ƒsw = 480 kHz, Equation 28 yields an input voltage ripple of 166 mV.
