ZHCSJ07A November 2018 – July 2019 LM25180
ADVANCE INFORMATION for pre-production products; subject to change without notice.
- 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 Integrated Power MOSFET
- 7.3.2 PSR Flyback Modes of Operation
- 7.3.3 Setting the Output Voltage
- 7.3.4 Control Loop Error Amplifier
- 7.3.5 Precision Enable
- 7.3.6 Configurable Soft Start
- 7.3.7 External Bias Supply
- 7.3.8 Minimum On-Time and Off-Time
- 7.3.9 Overcurrent Protection
- 7.3.10 Thermal Shutdown
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
Design 1: Wide VIN, Low IQ PSR Flyback Converter Rated at 5 V, 1 A
- 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 Custom Design With Excel Quickstart Tool
- 8.2.1.2.3 Flyback Transformer – T1
- 8.2.1.2.4 Flyback Diode – DFLY
- 8.2.1.2.5 Zener Clamp Circuit – DF, DCLAMP
- 8.2.1.2.6 Output Capacitor – COUT
- 8.2.1.2.7 Input Capacitor – CIN
- 8.2.1.2.8 Feedback Resistor – RFB
- 8.2.1.2.9 Thermal Compensation Resistor – RTC
- 8.2.1.2.10 UVLO Resistors – RUV1, RUV2
- 8.2.1.2.11 Soft-Start Capacitor – CSS
- 8.2.1.3 Application Curves
- 8.2.2 Design 2: PSR Flyback Converter With Dual Outputs of 15 V and –7.7 V at 200 mA
- 8.2.3 Design 3: PSR Flyback Converter With Stacked Dual Outputs of 24 V and 5 V
- 8.2.1
Design 1: Wide VIN, Low IQ PSR Flyback Converter Rated at 5 V, 1 A
- 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 External Bias Supply
Figure 22. External Bias Supply Using Transformer Auxiliary Winding The LM25180 has an external bias supply feature that reduces input quiescent current and increases efficiency. When the voltage at SS/BIAS exceeds a rising threshold of 5.5 V, bias power for the internal LDO regulator can be derived from an external voltage source or from a transformer auxiliary winding as shown in Figure 22. With a bias supply connected, the LM25180 then uses its internal soft-start ramp to control the primary current during start-up.
When using a transformer auxiliary winding for bias power, the total leakage current related to diodes DBIAS1 and DBIAS2 in Figure 22 should be less than 1 µA across the full operating temperature range.