ZHCSTL8F April 2007 – November 2023 LM25116
PRODUCTION DATA
- 1
- 1 特性
- 2 应用
- 3 说明
- 4 Pin Configuration and Functions
- 5 Specifications
- 6 Detailed Description
-
7 Application and Implementation
- 7.1 Application Information
- 7.2
Typical Application
- 7.2.1 Design Requirements
- 7.2.2
Detailed Design Procedure
- 7.2.2.1 Timing Resistor
- 7.2.2.2 Output Inductor
- 7.2.2.3 Current Sense Resistor
- 7.2.2.4 Ramp Capacitor
- 7.2.2.5 Output Capacitors
- 7.2.2.6 Input Capacitors
- 7.2.2.7 VCC Capacitor
- 7.2.2.8 Bootstrap Capacitor
- 7.2.2.9 Soft Start Capacitor
- 7.2.2.10 Output Voltage Divider
- 7.2.2.11 UVLO Divider
- 7.2.2.12 MOSFETs
- 7.2.2.13 MOSFET Snubber
- 7.2.2.14 Error Amplifier Compensation
- 7.2.2.15 Comprehensive Equations
- 7.2.3 Application Curves
- 7.3 Power Supply Recommendations
- 7.4 Layout
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
7.2.2.5 Output Capacitors
The output capacitors smooth the inductor ripple current and provide a source of charge for transient loading conditions. For this design example, five 100-µF ceramic capacitors where selected. Ceramic capacitors provide very low equivalent series resistance (ESR), but can exhibit a significant reduction in capacitance with DC bias. From the manufacturer’s data, the ESR at 250 kHz is 2 mΩ / 5 = 0.4 mΩ, with a 36% reduction in capacitance at 5 V. This is verified by measuring the output ripple voltage and frequency response of the circuit. The fundamental component of the output ripple voltage is calculated with Equation 15.
Equation 16 calculates the typical values for the 5-V design example.
