Board usage recommendation

AN2620

16/20

Doc ID 13883 Rev 3

4.6

Layout considerations

The layout is an important step in the design for all switching power supplies.

The high-speed operation (900 kHz) of the ST1S10 device demands careful attention to the

PCB layout. Care must be taken in the board layout to obtain maximum device performance,

otherwise the regulator could show poor line and load regulation, stability issues as well as

EMI problems.

It is critical to provide a low inductance, impedance ground path. Therefore, use wide and

short traces for the main current paths.

The input capacitor must be placed as close as possible to the IC pins as well as the

inductor and output capacitor. Use a common ground node for power ground and a different

one for control ground (AGND) to minimize the effects of ground noise. Connect these

ground nodes together underneath the device and make sure that small signal components

routed away from noisy components and traces (e.g., SW line). Its trace should be

minimized and shielded by a guard-ring connected to the ground.

Figure 12.

PCB layout suggestion

V

Input capacitor C1 must be placed

as close as possible to the IC

pins as well as the inductor L1

and Output capacitor C2

Via holes from thermal pad

To bottom layer

Input Sync

Enable/

Disable

Input Power Supply

Output Voltage

V

Input capacitor C1 must be placed

as close as possible to the IC

pins as well as the inductor L1

and Output capacitor C2

Via holes from thermal pad

To bottom layer

Input Sync

Enable/

Disable

Input Power Supply

Output Voltage