A good PCB layout for optimal thermal performance involves placing the device near a thermal pad or a heat sink, and ensuring good thermal conductivity between the device and the heat sink. A 2-layer or 4-layer PCB with a solid ground plane is recommended. Avoid placing thermal vias under the device, and keep the thermal pad clear of any components or traces.
To ensure reliable start-up, ensure that the input voltage rises monotonically and does not droop during start-up. A soft-start circuit can be used to limit the inrush current and prevent voltage droop. Additionally, ensure that the output voltage is properly decoupled with a capacitor to prevent oscillations.
The recommended input capacitor value is 10uF to 22uF, with a voltage rating of 50V or higher. A low-ESR ceramic capacitor such as X5R or X7R is recommended. Avoid using electrolytic capacitors as they may not provide sufficient ripple current capability.
The compensation network can be optimized by using the TI's Power Stage Designer tool or by following the guidelines in the datasheet. A Type II compensation network is recommended, with a zero at 1/3 to 1/2 of the switching frequency and a pole at 1/2 to 2/3 of the switching frequency.
The maximum allowed output voltage ripple is 1% of the nominal output voltage. Exceeding this limit may affect the stability and reliability of the converter. A good design practice is to aim for an output voltage ripple of 0.5% or less.
UCC28C40DGKR datasheet
by Texas Instruments
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