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
7.2.2.9 Soft Start Capacitor
The capacitor at the SS pin (CSS) determines the soft-start time, which is the time for the reference voltage and the output voltage to reach the final regulated value. The soft-start time tSS must be substantially longer than the time required to charge COUT to VOUT at the maximum output current. To meet this requirement, use Equation 22.
Equation 22. tSS > VOUT × COUT / (ICURRENT LIMIT – IOUT)
The value of CSS for a given time is determined with Equation 23.
Equation 23. 
For this application, a value of 0.01 µF was chosen for a soft-start time of 1.2 ms.