This post covers key takeaways and frequently asked questions for ADIs Silent Switcher Technology. Links to the Webinar, Resources, and Related Content are at the end of the post. PowerPoint presentation will be provided for customers that register to watch the recorded webinar.
Webinar Information
Company Name: ADI (Analog Devices Inc.)
Training Date: 2/16/2023
Presenter: Daniel Cheng - Senior Manager, Design Engineering
- Daniel Cheng is a Senior Manager in the multimarket power business unit at ADI. He leads the team that develops hi-performance step down switching regulators and innovative Silent Switcher Technology. He joined Linear Technology in 2007 and has been with ADI since the acquisition in 2017. He received his Electrical Engineering in Computer Science Degree from the University of California, Berkeley.
SS Tech - Snip from Webinar Presentation
Key Takeaways:
1) Silent Switcher 1 Types
- Ultralow EMI emissions
- High Efficiency at High Switching Frequency(fsw)
2) Silent Switcher 2 Types (Next Generation)
- Integrated Capacitors for a small solution size
- The hot loops are ground plane inside which Lower’s EMI
- Fewer external components, helps to eliminate PCB layout sensitivity
3) Silent Switcher 3 Types (New)
- Same benefits as SS2 but with improved Ultalow LF Noise in the range (0.1Hz to 100kHz)
- Ultrafast Transient Response
ADI’s Patented Silent Switcher® Technology has a reduced parasitic inductance with the internal design change from bond wire to flip chip with copper pillars. The Energy in the harmonics have been reduced by splitting the “hot loops” into two smaller loops. EMI prevention is performed by having the two loops cancel out each others fields. With the internal switch drivers, the switching power loss is minimized providing fast, clean switching edges. The focus in this webinar is on the SS (Silent Switcher) Technology for (SS1, SS2, and SS3). The SS-PMBus family has additional digital programmability telemetry via PMBus. This family will be addressed at a later time.
SS Snip from Webinar Presentation
The Copper Pillar Flip-Chip design with Magnetic Cancelation technology, as implemented in the LT8614, offers significant improvements to Switch-Node Ringing over the older wire-bonded chip design, such as the LT8610. Refer to the graphs below.
Snip’s from Webinar Presentation
The results of the EMI radiated noise test conducted between the Flip-Chip design and the old wire-bond show a significant improvement, with a reduction of 10-20dB.
SS Snip from Webinar Presentation
The sign switcher powertrain is an innovative technology that achieves near-zero deadtime, which refers to the period when both power FETs are turned off just before the rising switch edge. This reduction in deadtime results in significantly lower power loss since there is no body diode conduction, and the reverse recovery charge is minimized. As a result, the sign switcher powertrain provides better efficiency at high switching frequencies and enables more controlled switching edges.
SS Snip from Webinar Presentation
The SS2 is the Next-Generation switcher that comes in an LQFN package and features integrated capacitors. One of its key advantages is that all hot loops are grounded, which reduces electromagnetic interference (EMI). Additionally, the integrated capacitors reduce the number of external capacitor components required, resulting in a smaller solution size and eliminating the need for PCB layout sensitivity. Moreover, the Silent Switcher SP types have an exposed thick die, which improves thermal performance and allows for better heat transfer to a heatsink. These features make the SS2 a highly attractive option for those seeking higher efficiency in their electronic applications.
SS2 Snip from Webinar Presentation
The New SS3 was designed to tackle ultralow LF (low frequency) noise between 0.1Hz to 100kHz. The type of noise being referred to is the inherent device noise, or thermal noise. The SS3 can be used as a replacement for an LDO (low dropout regulator), providing a more efficient alternative. Moreover, this switcher is capable of direct drive, which means it can drive loads directly without requiring additional external components.
SS3 Snip from Webinar Presentation
For quick reference here is the SS Family Portfolio. Also note, SS3 Series is currently being expanded on with higher voltages and current.
SS Snip from Webinar Presentation
Q&A
How to reduce HF (High Frequency) Switching Noise?
By increasing the switching frequency (fsw) of the component, it becomes possible to utilize smaller external components (such as Cin, Cout, and L), achieving a higher loop bandwidth for faster response times, and accommodate automotive applications that require switching frequencies greater than 1.8MHz, which is above the AM radio band.
Why Zero Deadtime?
With high frequency switching, there is less power loss(body diode conduction) and minimal reverse recovery charge.
Do you plan to produce switchers like this one that can handle Vin of 60V or more, considering that numerous industries are transitioning to the 48V bus?
Yes! Possible options are LT8641, LT8645S, etc.
Regarding the converter’s Burst Mode, how does it affect the noise? “I frequently work on designs involving signal conditioning within the 10-100 kHz range, and I’ve observed that Burst Mode or Light Load modes may cause the switching frequency bursts to drift down into the signal range, resulting in interference within the 10-100 kHz range.”
That is true. If your application is very sensitive to 10-100khz, I’d recommend not using Burst Mode operation, and using FCM (Forced Continuous Mode) instead. Unfortunately you trade-off low load efficiency by doing this. Stay tuned for the Silent Switcher 3 discussion, which may be very interesting for your signal conditioning applications!
Is a heat sink or large copper area required on the PCB?
Thermal performance is always somewhat PCB dependent. Datasheet curves/specs are based on the standard evaluation board, which are typically 4-layer ~ 4"x3" PCBs. Outside of the SP parts that were briefly mentioned, we do not rely on heat sinks for the thermal performance data.
What is LDO?
Low Dropout Regulator (or linear regulator)
What are the disadvantages of the new chips?
The primary thing to note about SS3 is that in order to achieve low noise, it needs to consume more quiescent current (iq). Therefore, the very low load efficiency will not be as good as compared to our ultralow iq SS1 and SS2 parts.
Does the SS3 maintain its LF (Low Frequency) noise performance even under light load?
Customers typically use these parts in Forced Continuous Mode (FCM) in order to keep the programmed full fsw, even at light load. (Tradeoff is worse low load efficiency)
Are there any plans for SS3 for higher voltage applications (Vin> 42V)?
Yes! 40Vin / <2A SS3 is on the roadmap and coming shortly. 1A 18V SS3 parts are coming too.
Are Silent Switchers made for Aerospace or RAD HARD (Radiation Hardened) applications?
The SS3 are not RAD Hard qualified, but have shown to have passed RAD HARD testing but are not currently available. Interested parties should contact space@analog.com
Is a heatsink or large copper area on the PCB needed?
Thermal performance is always somewhat PCB dependent. Datasheet curves/specs are based on the standard evaluation board, which are typically 4 layer ~4"x3" PCBs. Outside of the SP parts that were briefly mentioned, we do not rely on heat sinks for the thermal performance data.
What is the temperature range for the SS Family?
Our parts are typically -40C to 150C. Some parts are limited to 125C due to the temp rating of the integrated caps. There’s a limited number of parts that are rated down to -55C.
Are there evaluation development boards for the SS family?
Yes! Eval Boards can be found here
Is the datasheet available for the LT8625S?
There is a short version on analog.com. You can request a full datasheet there as well (requires a quick and easy customer NDA).
When Will Automotive AEC-Q100 parts become available?
The current availability can be viewed here on Digi-Key’s website
Links to Resources and Related Content:
Webinar: Achieving Ultra-low Noise Switch-Mode Power Supplies with ADI’s Silent Switcher Technology
Webinar Center: Webinars free, live and on demand | DigiKey
Silent Switcher Resources: Silent Switcher® Technology | Analog Devices
Analog Devices Supplier Center - Analog Devices Inc Distributor - ADI Supplier | DigiKey Electronics
Evaluation Boards -Evaluation Boards - DC/DC & AC/DC (Off-Line) SMPS | Electronic Components Distributor DigiKey