ZHCSD62F December 2012 – May 2021 LM25017
PRODUCTION DATA
- 1 特性
- 2 應用
- 3 說明
- 4 Revision History
- 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 Overview
- 7.3.2 VCC Regulator
- 7.3.3 Regulation Comparator
- 7.3.4 Overvoltage Comparator
- 7.3.5 On-Time Generator
- 7.3.6 Current Limit
- 7.3.7 N-Channel Buck Switch and Driver
- 7.3.8 Synchronous Rectifier
- 7.3.9 Undervoltage Detector
- 7.3.10 Thermal Protection
- 7.3.11 Ripple Configuration
- 7.3.12 Soft-Start
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1 Application Circuit: 12.5-V to 48-V Input and 10-V, 650-mA Output Buck Converter
- 8.2.2
Typical Isolated DC-DC Converter Using LM25017
- 8.2.2.1 Design Requirements
- 8.2.2.2
Detailed Design Procedure
- 8.2.2.2.1 Transformer Turns Ratio
- 8.2.2.2.2 Total IOUT
- 8.2.2.2.3 RFB1, RFB2
- 8.2.2.2.4 Frequency Selection
- 8.2.2.2.5 Transformer Selection
- 8.2.2.2.6 Primary Output Capacitor
- 8.2.2.2.7 Secondary Output Capacitor
- 8.2.2.2.8 Type III Feedback Ripple Circuit
- 8.2.2.2.9 Secondary Diode
- 8.2.2.2.10 VCC and Bootstrap Capacitor
- 8.2.2.2.11 Input Capacitor
- 8.2.2.2.12 UVLO Resistors
- 8.2.2.2.13 VCC Diode
- 8.2.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
封裝選項
機械數據 (封裝 | 引腳)
散熱焊盤機械數據 (封裝 | 引腳)
- DDA|8
訂購信息
8.2.1.2.6 Type III Ripple Circuit
Type III ripple circuit as described in Section 7.3.11 is chosen for this example. For a constant on time converter to be stable, the injected in-phase ripple should be larger than the capacitive ripple on COUT.
Using type III ripple circuit equations, the target ripple should be greater than the capacitive ripple generated at the primary output.
Cr = C6 = 3300 pF
Cac = C8 = 100 nF
For TON, refer to Equation 3.
Ripple resistor Rr is calculated to be 57.6 k?. This value provides the minimum ripple for stable operation. A smaller resistance should be selected to allow for variations in TON, COUT, and other components. Rr = R4 = 46.4 k? is selected for this example application.