ZHCSHZ8B april 2018 – february 2023 TPS62147 , TPS62148
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Parameter Measurement Information
-
9 Detailed Description
- 9.1 Overview
- 9.2 Functional Block Diagram
- 9.3 Feature Description
- 9.4
Device Functional Modes
- 9.4.1 Pulse Width Modulation (PWM) Operation
- 9.4.2 Power Save Mode Operation (PWM/PFM)
- 9.4.3 100% Duty-Cycle Operation
- 9.4.4 Current Limit And Short Circuit Protection (for TPS62148)
- 9.4.5 HICCUP Current Limit And Short Circuit Protection (for TPS62147)
- 9.4.6 Soft Start / Tracking (SS/TR)
- 9.4.7 Output Discharge Function (TPS62148 only)
- 9.4.8 Starting into a Pre-Biased Load
- 10Application and Implementation
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
10.1.4.3 Soft-Start Capacitor
A capacitor connected between SS/TR pin and GND sets user programmable start-up slope of the output voltage. A constant current source provides typically 2.5 µA to charge the external capacitance. The capacitor required for a given soft-start ramp time is given by:
Equation 14. 
where
- CSS is the capacitance required at the SS/TR pin and
- tSS is the desired soft-start ramp time
The fastest achievable typical ramp time is 150 µs even if the external Css capacitance is lower than 680 pF or the pin is open.