ZHCSNW4 October 2022 LM5012-Q1
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Control Architecture
- 8.3.2 Internal VCC Regulator and Bootstrap Capacitor
- 8.3.3 Regulation Comparator
- 8.3.4 Internal Soft Start
- 8.3.5 On-Time Generator
- 8.3.6 Current Limit
- 8.3.7 N-Channel Buck Switch and Driver
- 8.3.8 Schottky Diode Selection
- 8.3.9 Enable/Undervoltage Lockout (EN/UVLO)
- 8.3.10 Power Good (PGOOD)
- 8.3.11 Thermal Protection
- 8.4 Device Functional Modes
- 9 Application and Implementation
- 10Device and Documentation Support
- 11Mechanical, Packaging, and Orderable Information
8.3.5 On-Time Generator
The on time of the LM5012-Q1 high-side FET is determined by the RRON resistor and is inversely proportional to the input voltage, VIN. The inverse relationship with VIN results in a nearly constant frequency as VIN is varied. Use Equation 3 to calculate the on time.
Equation 3. 
Use Equation 4 to determine the RRON resistor to set a specific switching frequency in CCM.
Equation 4. 
Select RRON for a minimum on time (at maximum VIN) greater than 50 ns for proper operation. In addition to this minimum on time, the maximum frequency for this device is limited to 1 MHz.