ST1S14 datasheet(25/46 Pages) STMICROELECTRONICS

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ST1S14

Application information

high switching current loop areas should be kept as small as possible and lead lengths as

short as possible.

High impedance paths (in particular the feedback connections) are susceptible to

interference, so they should be as far as possible from the high current paths. A layout

example is provided in Figure 14 below.

The input and output loops are minimized to avoid radiation and high frequency resonance

problems. The feedback pin connections to the external divider are very close to the device

in order to avoid pick-up noise. Another important issue is the ground plane of the board. As

the package has an exposed pad, it is very important to connect it to an extended ground

plane in order to reduce the thermal resistance junction-to-ambient.

To increase the design noise immunity, different signal and power ground should be

implemented in the layout (see Section 7.5: Application circuit). The signal ground serves

the small signal components, the device ground pin, the exposed pad, and a small filtering

capacitor connected to the VCC pin. The power ground serves the external diode and the

input filter. The different grounds are connected underneath the output capacitor. Neglecting

the current ripple contribution, the current flowing through this component is constant during

the switching activity and so this is the cleanest ground point of the buck application circuit.

Figure 14. Layout example

ST1S14 数据表(PDF) 25 Page - STMicroelectronics