The UC2834DW 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 output inductor and diode should be placed close to the IC, and the output capacitors should be placed close to the load. A good rule of thumb is to keep the high-current paths short and wide, and to minimize the loop area of the switching node.
The selection of the inductor depends on the output current, output voltage, and switching frequency. TI recommends using an inductor with a low DC resistance (DCR) and a high saturation current. The inductor value should be chosen to achieve the desired output ripple voltage. A good starting point is to use an inductor with a value between 1-10 uH, and to adjust the value based on the output ripple voltage measurement.
The UC2834DW has an absolute maximum input voltage rating of 18V. However, the recommended operating input voltage range is 6-15V. Operating the IC above 15V may reduce its reliability and lifespan.
The UC2834DW requires a compensation network to ensure stability. TI recommends using a Type II compensation network, which consists of a resistor, a capacitor, and an optional zero. The compensation values depend on the output voltage, output current, and switching frequency. A good starting point is to use the values recommended in the datasheet, and to adjust them based on the loop gain measurement.
The bootstrap capacitor is used to generate the gate drive voltage for the high-side FET. It is charged through the bootstrap diode during the off-time of the high-side FET, and it provides the necessary voltage to turn on the FET during the on-time. The bootstrap capacitor value should be chosen to ensure that the gate drive voltage is sufficient to fully turn on the FET.
UC2834DW datasheet
by Texas Instruments
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