SNVS171J November 2001 – January 2017 LP2992
For best overall performance, place all circuit components on the same side of the circuit board and as near as practical to the respective LDO pin connections. Place ground return connections to the input and output capacitors, and to the LDO ground pin as close as possible to each other, connected by a wide, component-side, copper surface. The use of vias and long traces to create LDO circuit connections is strongly discouraged and negatively affects system performance. This grounding and layout scheme minimizes inductive parasitics, and thereby reduces load-current transients, minimizes noise, and increases circuit stability.
TI also recommends a ground reference plane either embedded in the PCB itself or located on the bottom side of the PCB opposite the components. This reference plane serves to assure accuracy of the output voltage, shield noise, and behaves similar to a thermal plane to spread (or sink) heat from the LDO device. In most applications, this ground plane is necessary to meet thermal requirements.
The WSON package requires specific mounting techniques which are detailed in AN-1187 Leadless Leadframe Package (LLP). Referring to the section PCB Design Recommendations, note that the pad style which must be used with the WSON package is the NSMD (non-solder mask defined) type.
The thermal dissipation of the WSON package is directly related to the printed circuit board construction and the amount of additional copper area.