11.1 Layout Guidelines

In all switching power supplies the layout is an important step in the design, especially at high peak currents and switching frequencies. If the layout is not carefully done, the regulator might show noise problems and duty cycle jitter.

The input capacitor should be placed as close as possible to the input pin for good input voltage filtering. The inductor and diode must be placed as close as possible to the switch pin to minimize noise coupling into other circuits. It is important to connect the output capacitor directly across the diode cathode pin and ground rather than connecting the output capacitor across the LEDs. This minimizes EMI. Because the feedback pin and network is a high-impedance circuit, the feedback network should be routed away from the inductor.

11.2 Layout Example

Figure 25. Layout Example

11.3 Thermal Considerations

The TPS61043 comes in a thermally enhanced QFN package. The package includes a thermal pad improving the thermal capabilities of the package. See QFN/SON PCB Attachment (SLUA271).

The thermal resistance junction to ambient R_ΘJA of the QFN package greatly depends on the PCB layout. Using thermal vias and wide PCB traces improves the thermal resistance R _ΘJA. Under normal operation conditions no PCB vias are required for the thermal pad. However, the thermal pad must be soldered to the PCB.