ZHCSFE2A August 2016 – November 2017 LM5161-Q1
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 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 Control Circuit
- 7.3.2 VCC Regulator
- 7.3.3 Regulation Comparator
- 7.3.4 Soft-Start
- 7.3.5 Error Transconductance (GM) Amplifier
- 7.3.6 On-Time Generator
- 7.3.7 Current Limit
- 7.3.8 N-Channel Buck Switch and Driver
- 7.3.9 Synchronous Rectifier
- 7.3.10 Enable / Undervoltage Lockout (EN/UVLO)
- 7.3.11 Thermal Protection
- 7.3.12 Ripple Configuration
- 7.4 Device Functional Modes
-
8 Applications and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
LM5161-Q1 Synchronous Buck (15-V to 95-V Input, 12-V Output, 1-A Load)
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1 Custom Design With WEBENCH® Tools
- 8.2.1.2.2 Output Resistor Divider Selection
- 8.2.1.2.3 Frequency Selection
- 8.2.1.2.4 Inductor Selection
- 8.2.1.2.5 Output Capacitor Selection
- 8.2.1.2.6 Series Ripple Resistor - RESR (FPWM = 1)
- 8.2.1.2.7 VCC and Bootstrap Capacitor
- 8.2.1.2.8 Input Capacitor Selection
- 8.2.1.2.9 Soft-Start Capacitor Selection
- 8.2.1.2.10 EN/UVLO Resistor Selection
- 8.2.1.3 Application Curves
- 8.2.2 LM5161-Q1 Isolated Fly-Buck (36-V to 72-V Input, 12-V, 12-W Isolated Output)
- 8.2.1
LM5161-Q1 Synchronous Buck (15-V to 95-V Input, 12-V Output, 1-A Load)
- 8.3 Do's and Don'ts
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
7.3.7 Current Limit
The LM5161-Q1 provides an intelligent current limit OFF-timer that adjusts the OFF-time to reduce foldback of the current limit. If the peak value of the current in the buck switch exceeds 1.6 A (typical) the present ON-time period is immediately terminated, and a non-resettable OFF-timer is initiated. The length of the OFF-time is controlled by the FB voltage and the input voltage VIN. As an example, when VFB = 0.1-V and VIN = 72-V, the OFF-time is set to 13 μs (typical). This condition would occur if the output is shorted or during the initial phase of start-up. In cases of output overload where the FB voltage is greater than zero volts (a soft short), the current limit OFF-time is reduced. Reducing the OFF-time during less severe overloads reduces the current limit foldback, overload recovery time, and start-up time. The current limit off-time, TOFF(CL) is calculated from Equation 5:
