ST1S14 STMicroelectronics, ST1S14 Datasheet - Page 23

• Manufacturer Part Number: ST1S14
• Description: Up to 3 A step down switching regulator
• Manufacturer: STMicroelectronics

ST1S14
7.2
Layout considerations
The layout of switching DC-DC converters is very important to minimize noise and
interference. Power-generating portions of the layout are the main cause of noise and so
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
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
to avoid pick-up noise. Another important issue is the ground plane of the board. Since 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
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 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
Figure 14
Doc ID 17977 Rev 1
Chapter 7.5: Application
below.
circuit). The signal ground serves
Application information
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