ZHCSJ42 December 2018 TPS54340B
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 Adjusting the Output Voltage
- 7.3.7 Enable and Adjusting Undervoltage Lockout
- 7.3.8 Internal Soft Start
- 7.3.9 Constant Switching Frequency and Timing Resistor (RT/CLK) pin)
- 7.3.10 Accurate Current Limit Operation and Maximum Switching Frequency
- 7.3.11 Synchronization to RT/CLK pin
- 7.3.12 Overvoltage Protection
- 7.3.13 Thermal Shutdown
- 7.3.14 Small Signal Model for Loop Response
- 7.3.15 Simple Small Signal Model for Peak-Current-Mode Control
- 7.3.16 Small Signal Model for Frequency Compensation
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Application: Buck Converter
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedures
- 8.2.2.1 Custom Design with WEBENCH® Tools
- 8.2.2.2 Selecting the Switching Frequency
- 8.2.2.3 Output Inductor Selection (LO)
- 8.2.2.4 Output Capacitor
- 8.2.2.5 Catch Diode
- 8.2.2.6 Input Capacitor
- 8.2.2.7 Bootstrap Capacitor Selection
- 8.2.2.8 Undervoltage Lockout Setpoint
- 8.2.2.9 Output Voltage and Feedback Resistors Selection
- 8.2.2.10 Minimum VIN
- 8.2.2.11 Compensation
- 8.2.2.12 Discontinuous Conduction Mode and Eco-mode Boundary
- 8.2.2.13 Power Dissipation
- 8.2.3 Application Curves
- 8.3 Other Applications
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文檔支持
- 12機械、封裝和可訂購信息
8.2.2.8 Undervoltage Lockout Setpoint
The undervoltage lockout (UVLO) can be adjusted using an external voltage divider on the EN terminal of the TPS54340. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power down or brownouts when the input voltage is falling. For the example design, the supply must turn on and start switching once the input voltage increases above 5.75 V (UVLO start). After the regulator starts switching, it should continue to do so until the input voltage falls below 4.5 V (UVLO stop).
Programmable UVLO threshold voltages are set using the resistor divider of RUVLO1 and RUVLO2 between VIN and ground connected to the EN terminal. Equation 4 and Equation 5 calculate the resistance values necessary. For the example application, a 365 kΩ between VIN and EN (RUVLO1) and a 86.6 kΩ between EN and ground (RUVLO2) are required to produce the 8-V and 6.25-V start and stop voltages.
