SLUS829G August 2008 – February 2020 UCC2897A
PRODUCTION DATA.
- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Device Options
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3 Feature Description
- 8.4 Device Functional Modes
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
封裝選項
機(jī)械數(shù)據(jù) (封裝 | 引腳)
散熱焊盤機(jī)械數(shù)據(jù) (封裝 | 引腳)
- RGP|20
訂購信息
8.3.1.10 SS/SD
A capacitor (CSS) connected between this pin and GND (pin 6) programs the soft-start time of the power converter. The soft-start capacitor is charged by a precise, internal DC-current source which is programmed by the RON resistor connected to pin 2. The soft-start current is defined in Equation 7.
This DC current charges CSS from 0 V to approximately 5 V. Internal to the UCC2897A, the soft-start capacitor voltage is buffered and ORed with the control voltage present at the FB pin (pin 9). The lower of the two voltages manipulates the PWM engine of the controller through the voltage divider described with regards to the FB pin. Accordingly, the useful control range on the SS pin is similar to the control range of the FB pin and it is between 2.5 V and 4.5 V approximately. During line-undervoltage protection, the PWM follows this pin-capacitor discharge to achieve soft-stop function