In noise-sensitive blocks like RF, high-speed data converters, and phase-locked loops (PLLs), power is more than just an auxiliary circuit. System performance is directly tied to power quality.

Kwon Ik-seung, managing director of Analog Devices Korea (ADI), has recently been focusing on the issue of power noise.
Having worked on RF, analog, and data converter applications for many years, he points out that designers are constantly faced with the same dilemma: choosing between LDOs and switching regulators. They want to use switching regulators for efficiency and heat dissipation, but they must stick with LDOs due to noise.

The message that Director Kwon emphasized in this interview is clear.
“Silent Switcher is bridging this gap.”
Sensitive nodes dominated by LDO

Power noise issues are particularly prominent in sensitive nodes such as PLLs, ADCs/DACs, and RF LNAs.

Director Kwon explained as follows:
“Because PLL power supplies are directly susceptible to noise and spurs, designers have unconditionally used LDOs. However, starting with the third-generation Silent Switcher, noise characteristics similar to those of an LDO were observed when combined with a small LC filter. This demonstrates the growing number of cases where switching is possible.

The same applies to the clock and reference power supplies of ADCs/DACs. While ripple suppression is essential for maintaining ENOB and SFDR, it's explained that comparable performance can be achieved by adding a small filter to the Silent Switcher. It also emphasized that spur suppression can simplify the design of extremely sensitive analog power supplies, such as RF LNAs and mixer bias.
Can we kill two birds with one stone: ensuring efficiency and power integrity?

The Silent Switcher's popularity stems from the industry's push to simultaneously achieve efficiency and power integrity. As equipment becomes smaller, the heat dissipation area shrinks, and the importance of efficiency grows. Managing Director Kwon explained that the smaller the equipment, the more serious the heat generation issue becomes. He explained that increasing efficiency leads to increased noise, while reducing noise inevitably leads to increased heat generation. He explained that the Silent Switcher can offer a balance between the two, and proposed two architectural strategies for securing the latest power integrity.

1. The external high voltage (48V/28V) is lowered to the intermediate bus (12V/18V) by an efficiency-oriented switching buck.
2. Afterwards, at each POL (Point of Load), a Silent Switcher (+LC) is used for sensitive nodes, and an LDO is used only for ultra-low current nodes.

In this way, blocks with low sensitivity can be processed in batches through switching, and only specific nodes such as PLL, clock, and ADC/DAC can be precisely managed.
Using modular Silent Switchers with built-in inductors also reduces layout risk and development time.
Case-by-case verification still needed

However, this does not mean that Silent Switchers replace LDOs in all situations.

"Design is always a case-by-case process. While a silent switcher can sometimes produce sufficient results, an LDO is still necessary when conditions aren't right. As an engineer, verification is essential."
― Executive Director Kwon Ik-seung

In particular, LDOs with excellent low-frequency noise floor (10 Hz to 10 kHz) and mid-low frequency PSRR are still advantageous. In addition, increasing the switching frequency of the Silent Switcher to several MHz or more makes it easier to suppress spurs with a small LC, but at the same time, there are trade-offs such as increased switching loss, increased heat generation, and shift in the EMI spectrum.

In other words, he explains that Silent Switcher is not a “one-size-fits-all solution,” but rather a valid option for finding a balance between efficiency, power integrity, EMI, and thermal management.
Checkpoints for practitioners to remember

The checkpoints that Director Kwon emphasized to field engineers are specific.

- Identify sensitive nodes first, such as PLL, clock, reference, ADC/DAC, and RF LNA.
- When increasing the switching frequency, efficiency/heat generation/EMI tradeoffs should be considered together.
- An LC or Ferrite filter must be placed at the output terminal.
- Input capacitors should be placed as close as possible, minimizing the hot loop area and GND return path.
- Measurements will be made in the following order: power spectrum → system indicators (phase noise/SFDR/SNR) → transient response/load fluctuation → heat/efficiency → EMI.
- The impact of light load mode (Burst/Skip) on sensitive nodes will also be separately examined.

In particular, modular Silent Switchers with built-in inductors have the advantage of reducing layout burden, but BOM cost, thermal characteristics, and peak current limits must also be reviewed.
The mechanism and differentiation of Silent Switchertrong>

The Silent Switcher is a patented architecture by ADI. Its core lies in symmetrically separating the input hot loop to offset magnetic flux. This reduces EMI emissions and improves the overshoot and undershoot of the switching waveform.

"The Silent Switcher started out with EMI suppression. The loops are arranged symmetrically to capture magnetic flux. In the third-generation product, we improved the control loop to address low-frequency noise and transient response."
― Executive Director Kwon Ik-seung

Although competitors are attempting similar things, he says, “Silent Switcher’s performance differentiation still holds up.”
Conclusion: Verification is still needed, not certainty.

Silent Switchers are responding to the field's need to simultaneously achieve efficiency and power integrity. However, market adoption remains limited.

"I'm a designer myself, but I'm not yet 100% confident in saying, 'Use Silent Switchers over LDOs.' More success stories need to be accumulated. However, it's clearly showing promise, and I expect it to be tried and tested in more fields in the future."

Power is no longer simply a secondary circuit. Silent Switchers are introducing a new balance in power design. Engineers now have the option of “switching but being quiet.”
Editor's Note

Silent Switcher performance may vary depending on layout, load, temperature, and filter design conditions. The examples mentioned in this article represent specific environmental conditions and may not apply to all situations.