SBVS343A March   2019  – September 2019

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Pin Configuration and Functions
6. Specifications
7. Detailed Description
1. 7.1 Overview
2. 7.2 Functional Block Diagram
3. 7.3 Feature Description
4. 7.4 Device Functional Modes
8. Application and Implementation
1. 8.1 Application Information
2. 8.2 Typical Application
1. 8.2.1 Design Requirements
2. 8.2.2 Detailed Design Procedure
3. 8.2.3 Application Curves
9. Power Supply Recommendations
10. 10Layout
11. 11Device and Documentation Support
1. 11.1 Device Support
1. 11.1.1 Development Support
2. 11.1.2 Device Nomenclature
2. 11.2 Documentation Support
4. 11.4 Community Resources
6. 11.6 Electrostatic Discharge Caution
7. 11.7 Glossary
12. 12Mechanical, Packaging, and Orderable Information

• PWP|14
• PWP|14

#### 8.2.2.3.1 ISHUNT Calculations for the Typical Design

Given the maximum AC supply voltage and the minimum frequency for this application example, the calculated ISHUNT current using Equation 1 from the Standby Power and Output Efficiency section yields:

Equation 12. ISHUNT = 265 × 2 × π × 53 × 330 × 10-9 = 0.02912 A

NOTE

The Recommended Operating Conditions table does not specify the maximum AC voltage that can be used because the maximum VAC voltage is bound by the maximum ISHUNT current and the availability of the high-voltage cap-drop capacitor.

The RMS power given in Equation 13 and the peak power given in Equation 14 must be used to determine the power rating of the surge resistor RS.

Equation 13. PRMS = (ISHUNT ) 2 × RS
Equation 14. PPEAK = [ISHUNT × RS + 4(VLDO_OUT (nom) + 0.6 V)]2 / RS

Using Equation 13 and Equation 14 yields the following RS power ratings:

Equation 15. PRMS = (0.02912)2 × 400 = 0.34 W
Equation 16. PPEAK = [0.02912 × 400 + 4(3.3 + 0.6 )]2 / 400 = 1.86 W

Use the power rating resulting from Equation 14 because this equation yields a higher power requirement. Furthermore, additional margin is always a good design practice.