UCC2895 Layout and Grounding （UCC2895布局和接地）.pdf

Application Report SLUA501 – April 2008 UCC2895 Layout and Grounding Recommendations John Bottrill ABSTRACT The UCC2895 family of Phase Shifted Full Bridge Power Converters Control Circuits are designed to provide efficient power conversion with minimal noise generation. This is accomplished by the resonant switching of the primary side voltages, which minimizes the switching losses and the voltage/current transients that would be present in a hard switched conventional full bridge power supply. 1 Overview Though resonant converters minimize the generation of noise in power circuits, the designer must take care in the layout and grounding of the converter’s control circuit to limit the noise introduced into the device. The UCC2895 has features to help with this. Any significant noise on the incoming signal lines will result in misinterpretation by the control loop. Without a clear, strong control signal, the converter may not respond as desired. This application note explains how to avoid noise problems when using these controllers. 2 Grounding There are two separate ground planes around the controller, the power ground plane and the signal ground plane. The ground connections to the power circuitry are accomplished over the power ground plane, which connects to the PGND pin. UCC2895 pins VCC, OUTA, OUTB, OUTC and OUTD are located over the power ground plane. The signal ground plane is reference for the control circuitry, including operational am