ZHCSIQ0F August 2018 – August 2020 TPS2120 , TPS2121
PRODUCTION DATA
- 1 特性
- 2 應用
- 3 說明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Parameter Measurement Information
-
9 Detailed Description
- 9.1 Overview
- 9.2 Functional Block Diagram
- 9.3
Feature Description
- 9.3.1 Input Settling Time and Output Soft Start Control (SS)
- 9.3.2 Active Current Limiting (ILM)
- 9.3.3 Short-Circuit Protection
- 9.3.4 Thermal Protection (TSD)
- 9.3.5 Overvoltage Protection (OVx)
- 9.3.6 Fast Reverse Current Blocking (RCB)
- 9.3.7 Output Voltage Dip and Fast Switchover Control (TPS2121 only)
- 9.3.8 Input Voltage Comparator (VCOMP)
- 9.4 TPS2120 Device Functional Modes
- 9.5 TPS2121 Device Functional Modes
- 10Application and Implementation
- 11Power Supply Recommendations
- 12Layout
- 13Device and Documentation Support
- 14Mechanical, Packaging, and Orderable Information
10.2.4.3 Selecting Soft-Start Capacitor and Current Limit Resistors
Equation 1 can be used to determine the RLIM values for this application. In this example, the DC load current is 1 A. Setting the current limit to 2 A will limit potential inrush current events and protect downstream loads. See Equation 8 for the TPS2120 ILM Calculation:
See Equation 9 for the TPS2121 ILM Calculation:
To calculate the slew rate needed to limit the inrush current to 100 mA, the Slew Rate Calculation can be used in Equation 10:
Using this equation, the slew rate must be limited to 1000V/S or below to keep the inrush current below 100 mA. According to Table 9-1, at 5 V a CSS capacitance of 100 nF will provide a slew rate of 780V/S (typical), which is below the calculated threshold of 1000V/S. Therefore, a 100 nF capacitor will limit the inrush below 100 mA in a typical application.