ZHCSF14D March 2010 – October 2018 TPS54260
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 Output Current
- 7.3.3 Pulse-Skip Eco-Mode
- 7.3.4 Low-Dropout Operation and Bootstrap Voltage (BOOT)
- 7.3.5 Error Amplifier
- 7.3.6 Voltage Reference
- 7.3.7 Adjusting the Output Voltage
- 7.3.8 Enable and Adjusting Undervoltage Lockout
- 7.3.9 Slow-Start / Tracking Pin (SS/TR)
- 7.3.10 Overload Recovery Circuit
- 7.3.11 Sequencing
- 7.3.12 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
- 7.3.13 Overcurrent Protection and Frequency Shift
- 7.3.14 Selecting the Switching Frequency
- 7.3.15 How to Interface to RT/CLK Pin
- 7.3.16 Powergood (PWRGD Pin)
- 7.3.17 Overvoltage Transient Protection
- 7.3.18 Thermal Shutdown
- 7.3.19 Small Signal Model for Loop Response
- 7.3.20 Simple Small Signal Model for Peak Current Mode Control
- 7.3.21 Small Signal Model for Frequency Compensation
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
3.3-V Output Application
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1 Custom Design With WEBENCH® Tools
- 8.2.1.2.2 Selecting the Switching Frequency
- 8.2.1.2.3 Output Inductor Selection (LO)
- 8.2.1.2.4 Output Capacitor
- 8.2.1.2.5 Catch Diode
- 8.2.1.2.6 Input Capacitor
- 8.2.1.2.7 Slow-Start Capacitor
- 8.2.1.2.8 Bootstrap Capacitor Selection
- 8.2.1.2.9 Undervoltage Lock Out Set Point
- 8.2.1.2.10 Output Voltage and Feedback Resistors Selection
- 8.2.1.2.11 Compensation
- 8.2.1.2.12 Discontinuous Mode and Eco-Mode Boundary
- 8.2.1.2.13 Power Dissipation Estimate
- 8.2.1.3 Application Curves
- 8.2.2 Inverting Power Supply
- 8.2.3 Split-Rail Power Supply
- 8.2.4 12-V to 3.8-V GSM Power Supply
- 8.2.5 24-V to 4.2-V GSM Power Supply
- 8.2.1
3.3-V Output Application
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文檔支持
- 12機械、封裝和可訂購信息
封裝選項
機械數據 (封裝 | 引腳)
散熱焊盤機械數據 (封裝 | 引腳)
訂購信息
8.2.1.2.7 Slow-Start Capacitor
The slow-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 a load requires a controlled voltage slew rate. This is also used if the output capacitance is large and would require large amounts of current to quickly charge the capacitor to the output voltage level. The large currents necessary to charge the capacitor may make the TPS54260 reach the current limit or excessive current draw from the input power supply may cause the input voltage rail to sag. Limiting the output voltage slew rate solves both of these problems.
The slow-start time must be long enough to allow the regulator to charge the output capacitor up to the output voltage without drawing excessive current. Equation 40 can be used to find the minimum slow-start time, tss, necessary to charge the output capacitor, Cout, from 10% to 90% of the output voltage, Vout, with an average slow-start current of Issavg. In the example, to charge the effective output capacitance of 72.4 µF up to 3.3 V while only allowing the average output current to be 1 A would require a 0.19-ms slow-start time.
Once the slow-start time is known, the slow-start capacitor value can be calculated using Equation 6. For the example circuit, the slow-start time is not too critical since the output capacitor value is 2 x 47 μF which does not require much current to charge to 3.3 V. The example circuit has the slow-start time set to an arbitrary value of 3.5 ms which requires a 8.75-nF slow-start capacitor. For this design, the next larger standard value of 10 nF is used.
