By hvhipot 
Many digital systems suffer from excessive power noise at frequencies related to the system clock. Can a series resonant (also known as variable frequency resonant) circuit be connected between the power and ground layers as shown below to reduce this noise? The answer is affirmative. However, the circuit must meet the following unlikely conditions.
Firstly, the system clock frequency must be kept fixed. In clock systems that are not controlled by crystals,fluctuations in clock frequency may exceed ± 30%. Low power systems typically lower the clock frequency to reduce idle power consumption. High performance systems sometimes change speed to achieve performance. In diagnostic testing, the system clock is used to display any timing related faults. A power supply that adopts noise reduction strategies and carefully adjusts to the correct resonant frequency will not function properly under these conditions.
The attraction of series resonant circuits lies in their ability to use smaller capacitor values. The series resonance effect must be generated by matching the capacitor with appropriate inductance and resistance values. Unfortunately, the smaller the capacitor, the more complex the circuit.
For example, 1/5 of the typical value of a capacitor requires an error of ± 10% between the capacitor and inductor components. A capacitor with a typical value of 1/10 requires an error of ± 5%. And so on. It is difficult to achieve high-frequency inductors with such strict errors. If you think of a layout plan with fixed inductance and smaller capacitance values to place the series resonance point at the desired location, you will face the same difficulties. The precise values of capacitors and inductors are difficult to control.
In the following situations, the clock must play repeatedly without interruption or interval. When the clock stops, the resonant circuit will lose control and cause interference as severe as the problem being attempted to alleviate. When the clock restarts, the resonant circuit will need several clocks to catch up. There is no benefit during this period.
Resonant circuits are only useful for continuous stimulation and have no effect on preventing noise from random data events.
The series resonant circuit must be placed within a small wavelength segment of the device to be protected. Within this limited radius, the extended inductance of the power and ground layers will change the effective series inductance of the resonant circuit. Therefore, the accurate location of the resonant circuit is a very important issue. Therefore, without a complete redesign, the layout cannot be replaced. Even worse, a resonant component provides significant attenuation for the radiation of clock noise at one location, which may not benefit or even increase noise from other series resonances.
Finally, the resonant circuit only attenuates one frequency noise while keeping in mind that other harmonics of the clock rate are ineffective or small. In sine wave based systems such as FM or AM radio, resonant power components can provide truly surprising benefits.
When transitioning from two versions to the next, various clock speeds and the layout of the start and stop digital system are constantly changing, and the resonant power supply using filter components did not pass the test. It is best to use a digital power system when using large, simple, and resonant free capacitors.