ZHCS779B March 2012 – December 2023 UCC28070A
PRODUCTION DATA
- 1
- 1 特性
- 2 应用
- 3 说明
- 4 Pin Configuration and Functions
- 5 Specifications
-
6 Detailed Description
- 6.1 Overview
- 6.2 Functional Block Diagram
- 6.3
Feature Description
- 6.3.1 Interleaving
- 6.3.2 Programming the PWM Frequency and Maximum Duty-Cycle Clamp
- 6.3.3 Frequency Dithering (Magnitude and Rate)
- 6.3.4 External Clock Synchronization
- 6.3.5 Multi-phase Operation
- 6.3.6 VSENSE and VINAC Resistor Configuration
- 6.3.7 VSENSE and VINAC Open-Circuit Protection
- 6.3.8 Current Synthesizer
- 6.3.9 Programmable Peak Current Limit
- 6.3.10 Linear Multiplier and Quantized Voltage Feed Forward
- 6.3.11 Enhanced Transient Response (VA Slew-Rate Correction)
- 6.3.12 Voltage Biasing (VCC and VVREF)
- 6.3.13 PFC Enable and Disable
- 6.3.14 Adaptive Soft Start
- 6.3.15 PFC Start-Up Hold Off
- 6.3.16 Output Overvoltage Protection (OVP)
- 6.3.17 Zero-Power Detection
- 6.3.18 Thermal Shutdown
- 6.3.19 Current Loop Compensation
- 6.3.20 Voltage Loop Compensation
- 6.4 Device Functional Modes
-
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 Output Current Calculation
- 7.2.2.2 Bridge Rectifier
- 7.2.2.3 PFC Inductor (L1 and L2)
- 7.2.2.4 PFC MOSFETs (M1 and M2)
- 7.2.2.5 PFC Diode
- 7.2.2.6 PFC Output Capacitor
- 7.2.2.7 Current-Loop Feedback Configuration (Sizing of the Current-Transformer Turns-Ratio and Sense Resistor (RS))
- 7.2.2.8 Current-Sense Offset and PWM Ramp for Improved Noise Immunity
- 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
6.3.2 Programming the PWM Frequency and Maximum Duty-Cycle Clamp
The PWM frequency and maximum duty-cycle clamps for both GDx outputs of the UCC28070A are set through the selection of the resistors connected to the RT and DMAX pins, respectively. The selection of the RT resistor (RRT) directly sets the PWM frequency (fPWM).
Equation 3. 
Once RRT has been determined, the DMAX resistor (RDMX) may be derived.
Equation 4. 
where
- DMAX is the desired maximum PWM duty-cycle