JAJSH18A March   2019  – September 2019

PRODUCTION DATA.

1. 特長
2. アプリケーション
3. 概要
1.     Device Images
4. 改訂履歴
5. 概要（続き）
6. Pin Configuration and Functions
7. Specifications
8. Detailed Description
1. 8.1 Overview
2. 8.2 Functional Block Diagram
3. 8.3 Feature Description
4. 8.4 Device Functional Modes
9. Application and Implementation
1. 9.1 Application Information
2. 9.2 Typical Application
1. 9.2.1 Design Requirements
2. 9.2.2 Detailed Design Procedure
3. 9.2.3 Application Curves
10. 10Power Supply Recommendations
11. 11Layout
12. 12デバイスおよびドキュメントのサポート
1. 12.1 デバイス・サポート
1. 12.1.1 開発サポート
2. 12.1.2 デバイスの項目表記
2. 12.2 ドキュメントのサポート
3. 12.3 ドキュメントの更新通知を受け取る方法
4. 12.4 コミュニティ・リソース
5. 12.5 商標
6. 12.6 静電気放電に関する注意事項
7. 12.7 Glossary
13. 13メカニカル、パッケージ、および注文情報

• PWP|14
• PWP|14

#### 9.2.2.4 Calculating the Bulk Capacitor CSCIN

The TPS7A78 uses a bulk capacitor CSCIN to smooth the rectified DC voltage ripple on the SCIN pin and to supply charge to the switched capacitor stage; see the 4:1 Switched-Capacitor Voltage Reduction section. The CSCIN capacitor also functions as a charge reservoir to hold-up the device output voltage for a period of time if the supply collapses. The minimum value of the CSCIN capacitor required can be calculated using Equation 17 through Equation 20, however these equations make the following assumptions to simplify the CSCIN capacitor calculation:

• The AC supply frequency is within ±5% of the nominal standard frequencies of 50 Hz and 60 Hz
• The voltage ripple on the SCIN pin is around from 0.5 V to 0.8 V.
• The AC impedance of the cap-drop capacitor CS is at least ten times lower than that of the bulk capacitor CSCIN and the surge resistor RS

Use Equation 17 for the FB 60-Hz VAC supply and Equation 18 for the HB 60-Hz VAC supply.

Equation 17. CSCIN = 0.0014 × IOUT
Equation 18. CSCIN = 0.0035 × IOUT

Use Equation 19 for the FB 50-Hz VAC supply and Equation 20 for the HB 50-Hz VAC supply.

Equation 19. CSCIN = 0.0017 × IOUT
Equation 20. CSCIN = 0.0041 × IOUT

where

• IOUT is the application load current

The calculated CSCIN capacitor from Equation 17 through Equation 20 represents the minimum value required for the application example. However, Equation 17 through Equation 20 do not account for capacitance derating for all operating conditions. Follow the manufacturer recommendation and guidelines to ensure the minimum required capacitance needed for the application. See the Input and Output Capacitors Requirements section for more details.