3.3V-5A Output DC-DC Converter with 10 to 24V Input

The project published here is a synchronous step-down DC/DC converter based on the RT7258 chip. The chip has integrated high-side internal power MOSFET and gate driver for a low-side external power MOSFET. The board delivers 3.3V DC – 5A output current from 10V to 24V input supply. The RT7258‘s current mode architecture allows the transient response to be optimized over a wide input voltage and load range. Cycle-by-cycle current limit provides protection against shorted outputs and softy-start eliminates input current surge during start-up.

Features

• Supply 10V to 24V DC
• Output 3.3V DC
• Load Current 5Amps
• Current Mode Control
• Switching Frequency 600Khz
• Up to 90% Efficiency
• Cycle-by-cycle Current Limit
• Input Under Voltage Lockout
• Output Under Voltage Protection
• Thermal Shutdown Protection, Threshold 150°C
• Output Power LED
• 4 x 2.5mm Mounting Holes
• PCB Dimensions 51.44 x 24.13 mm

Soft-Start (SS): An internal current source charges an internal capacitor to build the soft-start ramp voltage (VSS). The VFB voltage will track the internal ramp voltage during the soft-start interval. The typical soft-start time is 2ms.

Over Temperature Protection

The RT7258 features Over Temperature Protection (OTP) circuitry to prevent overheating due to excessive power dissipation. The OTP will shut down the switching operation when the junction temperature exceeds 150°C. Once the junction temperature cools down by approximately 20°C, the converter will resume operation. To maintain continuous operation, the maximum junction temperature should be lower than 125°C.

Connections

• CN1: Pin 1 = 10V to 24V DC Input, Pin 2 = GND
• CN2: Optional Connector for TO220 MOSFET
• CN3: Pin 1 = 3.3V / 5Amps Output, Pin 2 = GND
• D1: Output Power LED

Schematic

Parts List

Connections

Gerber View

Photos

Video

RT7258 Datasheet

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