ZHCSY68D October 2008 – April 2025 LM5574-Q1
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Pin Configuration and Functions
- 5 Specifications
- 6 Detailed Description
-
7 Application and Implementation
- 7.1 Application Information
- 7.2
Typical Application
- 7.2.1 Design Requirements
- 7.2.2
Detailed Design Procedure
- 7.2.2.1 Custom Design With WEBENCH? Tools
- 7.2.2.2 External Components
- 7.2.2.3 R3 (RT)
- 7.2.2.4 L1- Inductor
- 7.2.2.5 C3- Ramp Capacitor
- 7.2.2.6 C9 -Output Capacitor
- 7.2.2.7 D1 - Async Diode
- 7.2.2.8 C1- Input Capacitor
- 7.2.2.9 C8 - Vcc Capacitor
- 7.2.2.10 C7 - BST Capacitor
- 7.2.2.11 C4 - SS Capacitor
- 7.2.2.12 R5, R6 - Feedback Resistor
- 7.2.2.13 R1, R2, C2 - SD Pin Components
- 7.2.2.14 R4, C5, C6 - Compensation Components
- 7.2.3 Application Curves
- 7.3 Power Supply Recommendations
- 7.4 Layout
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
7.2.2.3 R3 (RT)
RT sets the oscillator switching frequency. Generally, higher frequency applications are smaller but have higher losses. Operation at 300kHz was selected for this example as a reasonable compromise for both small size and high efficiency. The value of RT for 300kHz switching frequency can be calculated by Equation 7.
Equation 7. 
The nearest standard value of 21k? was chosen for RT.