ZHCSK33G July 2008 – July 2019 LM3421 , LM3423
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Device Comparison
- 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 Current Regulators
- 8.3.2 Predictive Off-Time (PRO) Control
- 8.3.3 Average LED Current
- 8.3.4 Analog Dimming
- 8.3.5 Current Sense and Current Limit
- 8.3.6 Overcurrent Protection
- 8.3.7 Zero Current Shutdown
- 8.3.8 Control Loop Compensation
- 8.3.9 Start-Up Regulator
- 8.3.10 Overvoltage Lockout (OVLO)
- 8.3.11 Input Undervoltage Lockout (UVLO)
- 8.3.12 PWM Dimming
- 8.3.13 LM3423 Only: DPOL, FLT, TIMR, and LRDY
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Applications
- 9.2.1
Basic Topology Schematics
- 9.2.1.1 Design Requirements
- 9.2.1.2
Detailed Design Procedure
- 9.2.1.2.1 Operating Point
- 9.2.1.2.2 Switching Frequency
- 9.2.1.2.3 Average LED Current
- 9.2.1.2.4 Inductor Ripple Current
- 9.2.1.2.5 LED Ripple Current
- 9.2.1.2.6 Peak Current Limit
- 9.2.1.2.7 Loop Compensation
- 9.2.1.2.8 Input Capacitance
- 9.2.1.2.9 N-channel FET
- 9.2.1.2.10 Diode
- 9.2.1.2.11 Output OVLO
- 9.2.1.2.12 Input UVLO
- 9.2.1.2.13 PWM Dimming Method
- 9.2.1.2.14 Analog Dimming Method
- 9.2.2
LM3421 Buck-Boost Application
- 9.2.2.1 Design Requirements
- 9.2.2.2
Detailed Design Procedure
- 9.2.2.2.1 Operating Point
- 9.2.2.2.2 Switching Frequency
- 9.2.2.2.3 Average LED Current
- 9.2.2.2.4 Inductor Ripple Current
- 9.2.2.2.5 Output Capacitance
- 9.2.2.2.6 Peak Current Limit
- 9.2.2.2.7 Loop Compensation
- 9.2.2.2.8 Input Capacitance
- 9.2.2.2.9 N-channel FET
- 9.2.2.2.10 Diode
- 9.2.2.2.11 Input UVLO
- 9.2.2.2.12 Output OVLO
- 9.2.2.3 Application Curve
- 9.2.3 LM3421 BOOST Application
- 9.2.4 LM3421 Buck-Boost Application
- 9.2.5 LM3423 Boost Application
- 9.2.6 LM3421 Buck-Boost Application
- 9.2.7 LM3423 Buck Application
- 9.2.8 LM3423 Buck-Boost Application
- 9.2.9 LM3421 SEPIC Application
- 9.2.1
Basic Topology Schematics
- 10Power Supply Recommendations
- 11Layout
- 12器件和文档支持
- 13机械、封装和可订购信息
8.3.11.2 PWM Dimming and UVLO
Equation 28. 
When zero current shutdown and UVLO are implemented together, the EN pin can be used to escape UVLO. The nDIM pin pulls up to VIN when EN is pulled low. Therefore, if VIN is within the UVLO hysteretic window when EN is pulled high again, the controller starts-up even though VTURN-ON is not exceeded.