Created: Apr 16, 2017
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This reference design features a typical application circuit for the MIC28510 device. The MIC28510 is a synchronous DC-DC buck converter capable of handling DC inputs up to 75V. Its output voltage is variable from 24V down to 0.8V with an accuracy of +/-1%. The device can output up to 4A current with 95% efficiency. It also offers protection features to prevent damage during fault conditions. These includes undervoltage lockout, internal soft-start, foldback current limit, “hiccup" mode short-circuit protection, and thermal shutdown.
As shown in the circuit, the MIC28510 has three power supply pin inputs (PVIN, VDD, and PVDD). The PVIN pins are connected to the drain of the high-side internal N-Channel MOSFET which can accept 4.5V to 75V input. The connection of the capacitors between the PVIN pins and the power ground (PGND) should be kept short. The VDD pin provides power to the internal reference and control sections of the MIC28510 while the PVDD pin supplies the gate driver of the internal bottom MOSFET. In the circuit, a FCX493TA transistor with a 5.6V Zener diode are used to regulate the input voltage to approximately 5V and supply voltage to the VDD and PVDD pins. The SW pins which are all connected to the source of the high-side MOSFET and the drain of the low-side MOSFET are the device output pins. A portion the SW pins output is sent back to the FB pin through the network composed of R3, C10, L1, C12, and R4. The output voltage of the circuit depends on the resistance of R4 and the resistor between the FB pin and the ground. As shown in the circuit, there are eight resistor (R5-R12) that can be selected by shorting one of the headers (J2-J9) to select the output voltage. For example, if the pins of J9 are shorted, the output of the circuit is 5V.
The other pins of the MIC28510 are used for bootstrap (BST pin), current sense (CS pin), frequency setting (FS pin), and enable (EN pin). The EN pin is connected to header J10 together with the input voltage, output voltage, and the ground. Applying a HIGH signal (not above the VDD supply) to the EN pin will enable the device while applying a LOW signal disables the device. For low power applications, the header J10 can be used as power supply input and output port but for larger power applications, ST1 and ST2 screw terminals must be used. The MIC28510 can be used in applications such as distributed power systems, communication or networking infrastructure, industrial power, and solar energy.