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
7.3.10 Slow Start (SS/TR)
The device uses the lower voltage of the internal voltage reference or the SS/TR pin voltage as the reference voltage and regulates the output accordingly. A capacitor on the SS/TR pin to ground implements a slow-start time. The device has an internal pullup current source of 2.3 μA that charges the external slow-start capacitor. Equation 4 shows the calculations for the slow-start time (tSS, 10% to 90%) and slow-start capacitor (Css). The voltage reference (Vref) is 0.8 V and the slow-start charge current (Iss) is 2.3 μA.
When the input UVLO is triggered, the EN pin is pulled below 1.21 V or a thermal shutdown event occurs; the device stops switching and enters low current operation. At the subsequent power-up, when the shutdown condition is removed, the device does not start switching until it has discharged its SS/TR pin to ground ensuring proper soft-start behavior.