ZHCSA01H October 2011 – June 2019 LMR24210
PRODUCTION DATA.
- 1 特性
- 2 應(yīng)用
- 3 說(shuō)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 COT Control Circuit Overview
- 7.3.2 Start-up Regulator (VCC)
- 7.3.3 Regulation Comparator
- 7.3.4 Zero Coil Current Detect
- 7.3.5 Overvoltage Comparator
- 7.3.6 On-Time Timer, Shutdown
- 7.3.7 Current Limit
- 7.3.8 N-Channel Mosfet and Driver
- 7.3.9 Soft Start
- 7.3.10 Thermal Protection
- 7.3.11 Thermal Derating
- 8 Application and Implementation
- 9 Layout
- 10器件和文檔支持
封裝選項(xiàng)
機(jī)械數(shù)據(jù) (封裝 | 引腳)
- YPA|28
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
訂購(gòu)信息
7.3.6 On-Time Timer, Shutdown
The on-time of the LMR24210 main MOSFET is determined by the resistor RON and the input voltage VIN. It is calculated as follows:
The inverse relationship of ton and VIN gives a nearly constant frequency as VIN is varied. RON should be selected such that the on-time at maximum VIN is greater than 150 ns. The on-timer has a limiter to ensure a minimum of 150 ns for ton. This limits the maximum operating frequency, which is governed by the following equation:
The LMR24210 can be remotely shutdown by pulling the voltage of the EN pin below 1 V. In this shutdown mode, the SS pin is internally grounded, the on-timer is disabled, and bias currents are reduced. Releasing the EN pin allows normal operation to resume because the EN pin is internally pulled up.
Figure 17. Shutdown Implementation