ZHCSMS3 December 2020 TPS54622-EP
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Pin Configurations 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 Undervoltage Lockout
- 7.3.10 Adjustable Switching Frequency and Synchronization (RT/CLK)
- 7.3.11 Slow Start (SS/TR)
- 7.3.12 Power Good (PWRGD)
- 7.3.13 Output Overvoltage Protection (OVP)
- 7.3.14 Overcurrent Protection
- 7.3.15 Thermal Shutdown
- 7.3.16 Small Signal Model for Loop Response
- 7.3.17 Simple Small Signal Model for Peak Current Mode Control
- 7.3.18 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 Procedures
- 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 Undervoltage Lockout Setpoint
- 8.2.2.9 Output Voltage Feedback Resistor Selection
- 8.2.2.10 Compensation Component Selection
- 8.2.2.11 Fast Transient Considerations
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
7.3.16 Small Signal Model for Loop Response
Figure 7-4 shows an equivalent model for the device control loop which can be modeled in a circuit simulation program to check frequency response and transient responses. The error amplifier is a transconductance amplifier with a gm of 1300 μA/V. The error amplifier can be modeled using an ideal voltage controlled current source. The resistor ROUT(ea) (2.38 MΩ) and capacitor COUT(ea) (20.7 pF) model the open loop gain and frequency response of the error amplifier. The 1-mV AC voltage source between the nodes a and b effectively breaks the control loop for the frequency response measurements. Plotting a/c and c/b show the small signal responses of the power stage and frequency compensation respectively. Plotting a/b shows the small signal response of the overall loop. The dynamic loop response can be checked by replacing the RL with a current source with the appropriate load step amplitude and step rate in a time domain analysis.
Figure 7-4 Small Signal Model for Loop Response