DocID022998 Rev 4

21/35

ST1S31

Application information

35

The feedback pin (FB) connection to the external resistor divider is a high impedance node,

so the interference can be minimized by routing the feedback node with a very short trace

and as far as possible from the high current paths.

A single point connection from signal ground to power ground is suggested.

Thanks to the exposed pad of the device, the ground plane helps to reduce the thermal

resistance junction to ambient; so a large ground plane, soldered to the exposed pad,

enhances the thermal performance of the converter allowing high power conversion.

Figure 10. PCB layout example

AM11423v1

Input cap as

close as possible

to VINSW pin

Star center for common ground

Short FB trace

VINA derived from Cin

To avoid dynamic voltage drop

Between VINA and VINSW

Short high

switching

current loop

Via to connect the thermal pad

To bottom or inner ground plane