ZHCSCW5B August 2014 – September 2017 LM43600
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 简化电路原理图
- 5 修订历史记录
- 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 Fixed Frequency Peak Current Mode Controlled Step-Down Regulator
- 8.3.2 Light Load Operation
- 8.3.3 Adjustable Output Voltage
- 8.3.4 Enable (ENABLE)
- 8.3.5 VCC, UVLO and BIAS
- 8.3.6 Soft Start and Voltage Tracking (SS/TRK)
- 8.3.7 Switching Frequency (RT) and Synchronization (SYNC)
- 8.3.8 Minimum ON-Time, Minimum OFF-Time and Frequency Foldback at Dropout Conditions
- 8.3.9 Internal Compensation and CFF
- 8.3.10 Bootstrap Voltage (BOOT)
- 8.3.11 Power Good (PGOOD)
- 8.3.12 Overcurrent and Short-Circuit Protection
- 8.3.13 Thermal Shutdown
- 8.4 Device Functional Modes
-
9 Applications and Implementation
- 9.1 Application Information
- 9.2
Typical Applications
- 9.2.1 Design Requirements
- 9.2.2
Detailed Design Procedure
- 9.2.2.1 Custom Design With WEBENCH® Tools
- 9.2.2.2 Output Voltage Setpoint
- 9.2.2.3 Switching Frequency
- 9.2.2.4 Input Capacitors
- 9.2.2.5 Inductor Selection
- 9.2.2.6 Output Capacitor Selection
- 9.2.2.7 Feedforward Capacitor
- 9.2.2.8 Bootstrap Capacitors
- 9.2.2.9 VCC Capacitor
- 9.2.2.10 BIAS Capacitors
- 9.2.2.11 Soft-Start Capacitors
- 9.2.2.12 Undervoltage Lockout Setpoint
- 9.2.2.13 PGOOD
- 9.2.3 Application Performance Curves
- 10Power Supply Recommendations
- 11Layout
- 12器件和文档支持
- 13机械、封装和可订购信息
8.3.4 Enable (ENABLE)
Voltage on the ENABLE pin (VEN) controls the ON or OFF functionality of the LM43600. Applying a voltage less than 0.4 V to the ENABLE input shuts down the operation of the LM43600. In shutdown mode the quiescent current drops to typically 1.1 µA at VIN = 12 V.
The internal LDO output voltage VCC is turned on when VEN is higher than 1.2 V. The LM43600 switching action and output regulation are enabled when VEN is greater than 2.1 V (typical). The LM43600 supplies regulated output voltage when enabled and output current up to 0.5 A.
The ENABLE pin is an input and cannot be open circuit or floating. The simplest way to enable the operation of the LM43600 is to connect the ENABLE pin to VIN pins directly. This allows self-start-up of the LM43600 when VIN is within the operation range.
Many applications will benefit from the employment of an enable divider RENT and RENB in Figure 36 to establish a precision system UVLO level for the stage. System UVLO can be used for supplies operating from utility power as well as battery power. It can be used for sequencing, ensuring reliable operation, or supply protection, such as a battery discharge level. An external logic signal can also be used to drive EN input for system sequencing and protection.
Figure 36. System UVLO By Enable Dividers