All high-current switchers are sensitive to board layout; take care when designing the pc board. You’ll obtain the best results by using a multilayer board, so you can dedicate a single layer to ground plane. You should tie the “power” components (C1, C2, C16, D2, C12, C13, C14) directly to this ground plane and group these components so that the connection paths are as short as possible. You should connect the low-current ground, as Fig 1 shows, and then tie it to the power ground at a single point near C13. Finally, all traces in the switching power path (R5, Q3, and L1) must be as short as possible.
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