Texas Instruments recommends a compact layout with the UCC2805DG4 placed close to the input capacitors and the output inductor. The input capacitors should be placed between the input voltage and ground, and the output inductor should be placed between the output voltage and ground. Additionally, the layout should be designed to minimize loop areas and keep sensitive nodes away from noisy nodes.
The input capacitor should be chosen based on the input voltage ripple requirement, the input voltage range, and the operating frequency. A low-ESR capacitor with a high ripple current rating is recommended. The capacitor value should be chosen to ensure that the input voltage ripple is within the recommended range of 1-2% of the input voltage.
The maximum output current that the UCC2805DG4 can handle depends on the input voltage, output voltage, and the inductor value. The datasheet provides a graph that shows the maximum output current vs. input voltage and output voltage. As a general rule, the output current should be derated by 20-30% to ensure reliable operation.
The UCC2805DG4 requires a compensation network to ensure stability. The datasheet provides a recommended compensation network that consists of a resistor and a capacitor. The values of the resistor and capacitor depend on the input voltage, output voltage, and the inductor value. The compensation network should be adjusted to achieve a phase margin of at least 45 degrees and a gain margin of at least 10 dB.
The bootstrap capacitor is used to generate the gate drive voltage for the high-side FET. The bootstrap capacitor is charged from the input voltage through the bootstrap diode and is used to drive the high-side 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 high-side FET.
UCC2805DG4 datasheet
by Texas Instruments
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