DC/DC Conversion Step-Down (Buck) Switch-Mode Power Converters
The purpose of this module is to help you design different low-power applications and provide insight on how simple non-synchronous buck converters can be used to develop solutions for non-typical requirements. The following provides examples of converter applications that fulfill a variety of industry requirements.
MCP16301/H 36 V Input Voltage Non-Synchronous Buck Converter
The MCP16301 is a highly integrated, high-efficiency, fixed frequency, step-down DC-DC converter in a popular 6-pin SOT-23 package that operates from input voltage sources up to 30 V. Integrated features include a high-side switch, fixed frequency Peak Current Mode Control, internal compensation, peak current limit and overtemperature protection. Minimal external components are necessary to develop a complete step-down DC-DC converter power supply.
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• PIC® Microcontroller and dsPIC® Digital Signal Controller Bias Supply
• 24 V Industrial Input DC-DC Conversion
• Set-Top Boxes
• DSL Cable Modems
• Wall Cube Regulation
• SLA Battery-Powered Devices
• AC-DC Digital Control Power Source
• Power Meters
• D2 Package Linear Regulator Replacement
• Medical and Health Care
• Distributed Power Supplies
MCP16301 Non-Synchronous Buck Regulator Application Circuit Example
The MCP16301/H step-down converters operate over a wide input voltage range, up to 36 V maximum. Typical applications include generating a bias or VDD voltage for the PIC® microcontrollers, digital control system bias supply for AC-DC converters, 24 V industrial input and similar applications.
This circuit example offers up to 96% efficiency with a wide input voltage range (4.5 V to 30 V) and step-down to 3.3 V at 600 mA output. Output voltage is currently set at 3.3 V and can be adjusted to a wide range from 2 V to 15 V. The integrated N-channel switch offers low RDSon at 460 mΩ. The following diagrams show the MCP16301 load operation and efficiency, with a fixed 5 V output.
- The boost diode is used to provide a charging path from the low-voltage gate drive source, while the switch node is low. The boost diode blocks the high voltage of the switch node from feeding back into the output voltage when the switch is turned on, forcing the switch node high.
- A standard 1N4148 ultra-fast diode is recommended for its recovery speed, high voltage blocking capability, availability and cost. The voltage rating required for the boost diode is VIN.
- The efficiency of the converter is a function of the forward drop and speed of the freewheeling diode. A low forward drop Schottky diode is recommended. The current rating and voltage rating of the diode is application dependent. The diode voltage rating should be a minimum of VIN, plus margin. In the circuit example, a diode rating of 40 V should be used because the application is designed to have a maximum input of 30 V.