ZHCS901E May 2012 – September 2021 TPS55340
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
Boost Converter
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1 Custom Design with WEBENCH Tools
- 8.2.1.2.2 Selecting the Switching Frequency (R4)
- 8.2.1.2.3 Determining the Duty Cycle
- 8.2.1.2.4 Selecting the Inductor (L1)
- 8.2.1.2.5 Computing the Maximum Output Current
- 8.2.1.2.6 Selecting the Output Capacitors (C8, C9, C10)
- 8.2.1.2.7 Selecting the Input Capacitors (C2, C7)
- 8.2.1.2.8 Setting Output Voltage (R1, R2)
- 8.2.1.2.9 Setting the Soft-start Time (C7)
- 8.2.1.2.10 Selecting the Schottky Diode (D1)
- 8.2.1.2.11 Compensating the Control Loop (R3, C4, C5)
- 8.2.1.3 Application Curves
- 8.2.2
SEPIC Converter
- 8.2.2.1 Design Requirements
- 8.2.2.2
Detailed Design Procedure
- 8.2.2.2.1 Selecting the Switching Frequency (R4)
- 8.2.2.2.2 Duty Cycle
- 8.2.2.2.3 Selecting the Inductor (L1)
- 8.2.2.2.4 Calculating the Maximum Output Current
- 8.2.2.2.5 Selecting the Output Capacitors (C8, C9, C10)
- 8.2.2.2.6 Selecting the Series Capacitor (C6)
- 8.2.2.2.7 Selecting the Input Capacitor (C2, C7)
- 8.2.2.2.8 Selecting the Schottky Diode (D1)
- 8.2.2.2.9 Setting the Output Voltage (R1, R2)
- 8.2.2.2.10 Setting the Soft-start Time (C3)
- 8.2.2.2.11 MOSFET Rating Considerations
- 8.2.2.2.12 Compensating the Control Loop (R3, C4)
- 8.2.2.3 Application Curves
- 8.2.1
Boost Converter
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information
8.2.1.2.7 Selecting the Input Capacitors (C2, C7)
At least 4.7 µF of ceramic input capacitance is recommended. Additional input capacitance may be required to meet ripple and/or transient requirements. High-quality ceramic, type X5R or X7R are recommended to minimize capacitance variations over temperature. The capacitor must also have an RMS current rating greater than the maximum RMS input current of the TPS55340 calculated with Equation 22. The input capacitor must also be rated greater than the maximum input voltage. The input voltage ripple can be calculated with Equation 23.
In the design example, the input RMS current is calculated to be 191 mA. The chosen input capacitor is a 10-µF, 35-V, 1210 X7R with 3-mΩ ESR. Although one with a lower voltage rating can be used, a 35-V rated capacitor was chosen to limit the affects of dc bias and to allow the circuit to be rated for the entire input range of the TPS55340. The input ripple is calculated to be 30 mV. An additional 0.1-µF, 50-V, 0603 X5R is located close to the VIN and GND pins for extra decoupling.