ZHCSHY7A April 2018 – May 2018 UCC28742
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3 Feature Description
- 7.4 Device Functional Modes
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8 Applications and Implementation
- 8.1 Application Information
- 8.2
Typical Application
- 8.2.1 Design Requirements
- 8.2.2
Detailed Design Procedure
- 8.2.2.1 Custom Design With WEBENCH® Tools
- 8.2.2.2 VDD Capacitance, CDD
- 8.2.2.3 VDD Start-Up Resistance, RSTR
- 8.2.2.4 Input Bulk Capacitance and Minimum Bulk Voltage
- 8.2.2.5 Transformer Turns Ratio, Inductance, Primary-Peak Current
- 8.2.2.6 Transformer Parameter Verification
- 8.2.2.7 VS Resistor Divider and Line Compensation
- 8.2.2.8 Standby Power Estimate
- 8.2.2.9 Output Capacitance
- 8.2.2.10 Feedback Loop Design Consideration
- 8.2.3 Application Curves
- 8.3 Do's and Don'ts
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
8.2.2.9 Output Capacitance
The output capacitance value is typically determined by the transient response requirement. Equation 27 assumes that the switching frequency can be at the UCC28742 minimum of fSW(min).
Another consideration of the output capacitor(s) is the ripple voltage requirement. The output capacitors and their total ESR are the main factors to determine the output voltage ripple. Equation 28 provides a formula to determine required ESR value RESR, and Equation 28 provides a formula to determine required capacitance. The total output ripple is the sum of these two parts with scale factors and 10mV to consider other noise as shown in Equation 30,
Example: if require VRIPPLE = 70 mV, assume 0.81 × VRIPPLE_R = 1.15 × VRIPPLE_C = 30 mV, then RESR = 4.05 mΩ, and COUT = 643 µF, with assumption of LP = 700 µH, IPP(max) = 0.713 A, NPS = 13, VOCV = 5.3 V.