1. Filter capacitor.
Power supply is one of the important conditions for the mainboard to work stably. In order to stabilize the working voltage of each chip, the AC clutter in the power supply is filtered to the ground by using the capacitor in the circuit, which makes the voltage stable output. Some filter capacitors use patch capacitors, and some use electrolytic capacitors directly inserted. The filter capacitor must have one foot grounding. The EC6,EC8, ECI0 in figure 5 is the VCCP power supply filter capacitor, which is used to remove the AC interference components from the VCCP power supply to ensure the stable output of the VCCP voltage to the CPU power supply. If the capacitance is damaged, the output voltage will fluctuate, resulting in unstable CPU operation failure.
Fig.1 Filter capacitor application circuit
2. Coupling capacitors
Coupling capacitors usually use patch capacitors, which are used in PCI-E and SATA signal lines. Coupled capacitors in series in signal circuits are used to isolate DC and ensure high-speed AC signal transmission, as shown in figure 6. A row of patch capacitors above the PCI_E slot is the coupling capacitance on the PCI_E slot signal line, as shown in figure 7.
Fig.2 Coupled capacitor application circuit
Fig.3 There is a row of coupling capacitors above the PCI-E slot
3. Resonant capacitance.
The resonant capacitors are all chip capacitors, which are used only in the crystal oscillator circuit (see figure 4), between the two pins of the crystal oscillator and the GND, respectively. As shown in figure 5, the capacitor on the side of the crystal oscillator is the resonant capacitor. The capacitance of the resonant capacitor ranges from several pF to dozens of pF, and the appearance of the resonant capacitor is white than that of the other patch capacitors. The parameters of the resonant capacitance will affect the frequency and the output amplitude of the crystal oscillator.
Fig.4 Resonant capacitor application circuit Fig.5 Resonant capacitor