ZHCSEQ3D February 2016 – December 2022 LM5165
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 Integrated Power MOSFETs
- 7.3.2 Selectable PFM or COT Mode Converter Operation
- 7.3.3 COT Mode Light-Load Operation
- 7.3.4 Low Dropout Operation and 100% Duty Cycle Mode
- 7.3.5 Adjustable Output Voltage (FB)
- 7.3.6 Adjustable Current Limit
- 7.3.7 Precision Enable (EN) and Hysteresis (HYS)
- 7.3.8 Power Good (PGOOD)
- 7.3.9 Configurable Soft Start (SS)
- 7.3.10 Thermal Shutdown
- 7.4 Device Functional Modes
-
8 Applications and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1 Design 1: Wide VIN, Low IQ COT Converter Rated at 5 V, 150 mA
- 8.2.2 Design 2: Small Solution Size PFM Converter Rated at 3.3 V, 50 mA
- 8.2.3 Design 3: High Density 12-V, 75-mA PFM Converter
- 8.2.4 Design 4: 3.3-V, 150-mA COT Converter With High Efficiency
- 8.2.5 Design 5: 15-V, 150-mA, 600-kHz COT Converter
- 8.3 Power Supply Recommendations
- 8.4 Layout
- 9 Device and Documentation Support
- 10Mechanical, Packaging, and Orderable Information
8.2.2.2.2 Switching Frequency – LF
Tie RT to GND to select PFM mode of operation. The inductor, input voltage, output voltage, and peak current determine the pulse switching frequency of a PFM-configured LM5165. For a given input voltage, output voltage and peak current, the inductance of LF sets the switching frequency when the output is in regulation. Use Equation 19 to select an inductance of 47 μH based on the target PFM converter switching frequency of 350 kHz at 12-V input.
IPK(PFM) in this example is the peak current limit setting of 120 mA plus an additional 10% margin added to include the effect of the 100-ns peak current comparator delay. An additional constraint on the inductance is the 180-ns minimum on-time of the high-side MOSFET. Therefore, to keep the inductor current well controlled, choose an inductance that is larger than LF(min) using Equation 20 where VIN(max) is the maximum input supply voltage for the application, tON(min) is 180 ns, and IL(max) is the maximum allowed peak inductor current.
Choose an inductor with saturation current rating above the peak current limit setting, and allow for derating of the saturation current at the highest expected operating temperature.