ZHCSGO2H September 2003 – November 2018 LM5007
PRODUCTION DATA.
- 1 特性
- 2 應用
- 3 說明
- 4 修訂歷史記錄
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Application
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 Custom Design With WEBENCH® Tools
- 8.2.2.2 Custom Design With Excel Quickstart Tool
- 8.2.2.3 Feedback Resistors, RFB1 and RFB2
- 8.2.2.4 Switching Frequency Selection, RON
- 8.2.2.5 Buck Inductor, L1
- 8.2.2.6 Output Capacitor, COUT
- 8.2.2.7 Type I Ripple Circuit, RC
- 8.2.2.8 Input Capacitor, CIN
- 8.2.2.9 Current Limit, RCL
- 8.2.3 Application Curves
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文檔支持
- 12機械、封裝和可訂購信息
8.2.2.9 Current Limit, RCL
Resistor RCL sets the current limit off-timer according to Equation 5. The useable values tend to be in the range of 100 kΩ to 1 MΩ. Equation 15 specifies the off-time required for volt-second balance on the inductor in current limit.
where
- 225 ns is the current limit response time,
- VF is the forward voltage drop of the freewheeling power diode,
- VOUT is the output voltage,
- ILIM is the current limit,
- RDCR is the inductor DC resistance.
The programmed current limit off-time should be higher than the off-time needed for volt-second balance on the inductor. For a short at the output (VOUT = 0 V) and VF = 0.7 V, an inductor DCR of 390 mΩ or higher is needed to achieve volt-second balance at the maximum programmed current limit off-time of 17 µs. Using Equation 5, an RCL of greater than 10 kΩ can be used. Select a conservative value of 100 kΩ for this design.
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For step-by-step design procedures, circuit schematics, bill of materials, PCB files, simulation and test results of LM5007-powered implementations, refer to the TI Designs reference design library. |