The UC3879DWG4 is a high-frequency switching regulator, and proper layout and placement are crucial for its operation. TI recommends a 4-layer PCB with a solid ground plane, and the IC should be placed close to the input capacitors. The switching node (SW pin) should be kept away from sensitive nodes, and the output filter components should be placed close to the output pins.
The inductor selection depends on the output voltage, current, and switching frequency. TI recommends using a shielded inductor with a low DC resistance and high saturation current. The inductor value should be chosen to ensure that the peak inductor current is within the recommended range (typically 1.5 to 2.5 times the output current).
The UC3879DWG4 has an absolute maximum input voltage rating of 18V. However, the recommended operating input voltage range is 12V to 15V. Exceeding the maximum input voltage can damage the IC.
The UC3879DWG4 requires a compensation network to ensure stability. TI recommends using a Type II compensation network, which consists of a resistor, capacitor, and resistor (R-C-R) connected between the COMP pin and GND. The values of the compensation components depend on the output voltage, current, and switching frequency.
The bootstrap capacitor (CB) is used to generate the gate drive voltage for the internal power MOSFET. It is charged through the bootstrap diode (DB) during the off-time of the switch. The bootstrap capacitor value should be chosen to ensure that the gate drive voltage is sufficient to fully enhance the power MOSFET.
UC3879DWG4 datasheet
by Texas Instruments
