MCP16331 Step-Down DC-DC Converter

MCP16331 Step-Down (Buck) Converter

The Microchip MCP16331 is a highly-integrated, high-efficiency, fixed-frequency, step-down DC-DC converter in a popular 6-pin SOT-23 or 8-pin TDFN 2 x 3 package that operates from input voltage sources up to 50 V. Integrated features include a high-side switch, fixed frequency peak current mode control, internal compensation, peak current limit and over-temperature protection. Minimal external components are necessary to develop a complete step-down DC-DC converter power supply. High converter efficiency is achieved by integrating the current-limited, low-resistance, high-speed N-Channel MOSFET and associated drive circuitry. High-switching frequency minimizes the size of external filtering components, resulting in a small solution size. The MCP16331 can supply 500 mA of continuous current, while regulating the output voltage from 2.0 V to 24 V. An integrated, high-performance peak current mode architecture keeps the output voltage tightly regulated, even during input voltage steps and output current transient conditions that are common in power systems. The EN input is used to turn the device ON and OFF. While OFF, only a few µA of current are consumed from the input for power shedding and load distribution applications. This pin is internally pulled up, so the device will start even if the EN pin is left floating. Output voltage is set with an external resistive divider

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MCP16331 Features

  • Up to 96% Efficiency
  • Input Voltage Range: 4.4 V to 50 V
  • Output Voltage Range: 2.0 V to 24 V
  • 2% Output Voltage Accuracy
  • Minimum 500 mA Output Current
  • 500 kHz Fixed Frequency
  • Adjustable Output Voltage
  • Low Device Shutdown Current: 6 uA
  • Peak Current Mode Control
  • Internal Compensation
  • Internal Soft-Start
  • Cycle-by-Cycle Peak Current Limit
  • Under-voltage Lockout (UVLO): 4.1 V to Start; 3.6 V to Stop
  • Over-temperature Protection
  • Available Package: 6-Lead SOT-23, 8-Lead 2x3 TDFN

MCP16331 Target Applications

MCP16331 Block Digram

mcp16331-block-diagram.PNG

EN has an internal pull up, so the device will start even if the EN pin is left floating.

MCP16331 Pin Function Table

Symbol Description
SW Output switch node, connects to the inductor, freewheeling diode and the bootstrap capacitor
EN Enable pin. There is an internal pull up on the VIN. To turn the device off, connect EN to GND.
NC Not connected
GND Ground pin
VFB Output voltage feedback pin. Connect VFB to an external resistor divider to set the output voltage.
BOOST Boost voltage that drives the internal NMOS control switch. A bootstrap capacitor is connected between the BOOST and SW pins.
VIN Input supply voltage pin for power and internal biasing.
EP Exposed Thermal Pad

MCP16331 Application Example

MCP16331 operates over a wide input voltage range, up to 50 V maximum. Typical applications include generating a bias or VDD voltage for the PIC® microcontroller product line, digital control system bias supply for AC-DC converters, 24 V industrial input, and similar applications. The figure below shows an application example of converting 50 V VIN to 3.3 V VOUT.

MCP16331-application-example.PNG
Component Value
CIN 2 X 10 µF
COUT 2 X 10 µF
L 15 µH
RTOP 31.6 kΩ
RBOT 10 kΩ
FW Diode B1100
Boost Diode 1N4148
CB 100 nF
  • 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.
  • For low-boost voltage applications, a small Schottky diode with the appropriately rated voltage can be used to lower the forward drop increasing the boost supply for gate drive.

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