Recommendations; Printed Circuit Board; Component Position; Ground And Power Supply (Vdd ) - ST STM32C0 Series Getting Started

5

Recommendations

5.1

Printed circuit board

For technical reasons, it is best to use a multilayer printed circuit board (PCB) with a separate layer dedicated
to ground (V
SS
effect. For many applications, economical reasons prohibit the use of this type of board. In this case, the major
requirement is to ensure a good structure for ground and for the power supply.
5.2

Component position

A preliminary layout of the PCB must make separate circuits:
• High-current circuits
• Low-voltage circuits
• Digital component circuits
• Circuits separated according to their EMI contribution. This reduces cross-coupling on the PCB that
introduces noise.
5.3 Ground and power supply (V
Every block (noisy, low-level sensitive or digital) must be grounded individually and all ground returns must be to
a single point. Loops must be avoided or their area has to be minimized. To improve analog performance, the
decoupling capacitors must be placed as close as possible to the device.
The power supply must be implemented close to the ground line to minimize the area of supply loops. This
is because the supply loop acts as an antenna, and is therefore the main transmitter and receiver of EMI. All
component-free PCB areas must be filled with additional grounding to create a shield (especially when using
single-layer PCBs).
5.4

Decoupling

All power supply and ground pins must be properly connected to the power supplies. These connections,
including pads, tracks, and vias must have the lowest possible impedance. This is typically achieved with thick
track widths and, preferably, with the use of dedicated power supply planes in multilayer PCBs.
In addition, each power supply pair must be decoupled with 100 nF filtering ceramic capacitor and a chemical
capacitor of about 4.7 μF connected between the supply pins of the device. These capacitors need to be placed
as close as possible to or below the appropriate pins on the underside of the PCB. Typical values are 10 nF to
100 nF, but exact values depend on the application needs.
AN5673 - Rev 2
) and another dedicated to the V
DD
Figure 12.
Via to V
DD
supply. This provides good decoupling and a good shielding
DD
)
Figure 12 shows the typical layout of such a pair.
Typical layout for VDD / VSS pair
Via to V
SS
Cap.
V V
DD SS
AN5673
Recommendations
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