TIDUEP0 May 2020
- Description
- Resources
- Features
- Applications
- 1Design Images
- 2System Description
-
3System Overview
- 3.1 Block Diagram
- 3.2 Design Considerations
- 3.3
Highlighted Products
- 3.3.1 TPD4E05U06 4-Channel Ultra-Low-Capacitance IEC ESD Protection Diode
- 3.3.2 TPD2EUSB30 2-Channel ESD Solution for SuperSpeed USB 3.0 Interface
- 3.3.3 2.3.3 HD3SS3220 10Gbps USB 3.1 USB Type-C 2:1 MUX With DRP Controller
- 3.3.4 TPS54218 2.95V to 6V Input, 2A Synchronous Step-Down SWIFT™ Converter
- 3.3.5 TPS54318 2.95V to 6V Input, 3A Synchronous Step-Down SWIFT™ Converter
- 3.3.6 CSD19538Q3A 100V, N ch NexFET MOSFET™, single SON3x3, 49mOhm
- 3.3.7 LM3488 2.97V to 40V Wide Vin Low-Side N-Channel Controller for Switching Regulators
- 3.3.8 TPS61178 20-V Fully Integrated Sync Boost with Load Disconnect
- 3.3.9 LMZM23601 36-V, 1-A Step-Down DC-DC Power Module in 3.8-mm × 3-mm Package
- 3.3.10 TPS7A39 Dual, 150mA, Wide-Vin, Positive and Negative Low-Dropout (LDO) Voltage Regulator
- 3.3.11 TPS74201 Single-output 1.5-A LDO regulator, adjustable (0.8V to 3.3V), any or no cap, programmable soft start
- 3.3.12 LP5910 300-mA low-noise low-IQ low-dropout (LDO) linear regulator
- 3.3.13 LP5907 250-mA ultra-low-noise low-IQ low-dropout (LDO) linear
- 3.3.14 INA231 28V, 16-bit, i2c output current/voltage/power monitor w/alert in wcsp
- 3.4
System Design Theory
- 3.4.1 Input Section
- 3.4.2
Designing of SEPIC based High Voltage Supply
- 3.4.2.1 Basic Operation Principle of SEPIC Converter
- 3.4.2.2 Design of Dual SEPIC Supply using uncoupled inductors
- 3.4.2.3 Duty Cycle
- 3.4.2.4 Inductor Selection
- 3.4.2.5 Power MOSFET Selection
- 3.4.2.6 Output Diode Selection
- 3.4.2.7 Coupling Capacitor Selection
- 3.4.2.8 Output Capacitor Selection
- 3.4.2.9 Input Capacitor Selection
- 3.4.2.10 Programming the Output Voltage
- 3.4.3 Designing the Low Voltage Power Supply
- 3.4.4 Designing the TPS54218 through Webench Power Designer
- 3.4.5 ± 5V Transmit Supply Generation
- 3.4.6 System Clock Synchronization
- 3.4.7 Power and data output connector
- 3.4.8 System Current and Power Monitoring
- 4Hardware, Software, Testing Requirements, and Test Results
- 5Layout Guidelines
- 6Design Files
- 7Software Files
- 8Related Documentation
- 9About the Author
3.4.2.7 Coupling Capacitor Selection
The selection of SEPIC capacitor, Cs, depends on the RMS current, which is given by:
The SEPIC capacitor must be rated for a large RMS current relative to the output power. This property makes the SEPIC much better suited to lower power applications where the RMS current through the capacitor is relatively small (relative to capacitor technology). The voltage rating of the SEPIC capacitor must be greater than the maximum input voltage. Tantalum and ceramic capacitors are the best choice for SMT, having high RMS current ratings relative to size. Electrolytic capacitors work well for through-hole applications where the size is not limited and they can accommodate the required RMS current rating. The peak-to-peak ripple voltage on Cs (assuming no ESR):
A capacitor that meets the RMS current requirement would mostly produce small ripple voltage on Cs. Hence, the peak voltage is typically close to the input voltage.