10.1 Layout Guidelines

As for all switching power supplies, especially those providing high current and using high switching frequencies, layout is an important design step. If layout is not carefully done, the regulator could show instability as well as EMI problems. Therefore, use wide and short traces for high current paths. The input capacitor, C1 in the Typical Application, must not only to be close to the VIN pin, but also to the GND pin in order to reduce the input ripple seen by the device. The input capacitor, C4 in the Typical Application, must also be placed close to the inductor. C5 is the reference capacitor for the internal integration circuit. It must be placed as close between the REF and AGND pins as possible to prevent any noise insertion to the digital circuits. The LX pin carries high current with fast rising and falling edges. Therefore, the connection between the pin to the inductor and Schottky diode must be kept as short and wide as possible. It is also beneficial to have the ground of the output capacitor C2 close to the PGND pin because there is a large ground return current flowing between them. When laying out signal grounds, TI recommends using short traces separated from power ground traces, and connecting them together at a single point, for example on the DAP. The DAP must be soldered on to the PCB and connected to the GND pin of the device. An additional thermal via can significantly improve power dissipation of the device.

10.2 Layout Example