Are crystals a thing of the past? TI is utilizing bulk acoustic wave (BAW) technology to introduce the industry's first wireless, crystal-less MCU and a network synchronizer capable of 400-Gbps.

Currently, hardware design limits widespread IoT data collection. 100 Gigabits per second won't be sufficient for the amount of data IoT applications generate, and components like the quartz crystal clocking device in wireless MCUs introduce weaknesses like EMI and other environmental concerns.

According to Ray Upton, Vice President of Connected Microcontrollers at Texas Instruments, these limitations make the key question for IoT clear.

"How do I take massive amounts of microdata and bring it in to make smart decisions, to be able to create different capabilities?" he asks in an interview with AAC. 

TI just announced two products aiming to answer this question with breakthrough BAW integrations. The SimpleLink CC2652RB is a crystal-less wireless MCU, and the LMK05318 is a network synchronizer capable of 400-Gbps links.

Upton states, "We're integrating [BAW] technology into products that are going to enable a whole different level of performance."

 

What Is Bulk Acoustic Wave (BAW) Technology?

According to Upton, "Bulk acoustic wave is pretty simple to understand. We're converting electrical energy to mechanical acoustics."

Bulk acoustic wave moves signals vertically, with a piezoelectric thin film sandwiched between two electrode layers that serve as acoustic mirrors. When a frequency is introduced into the device, the structure resonates at 2.5Ghz. This resonator structure stores the maximum acoustic energy, doing so with a high electrical Q. The mechanical vibration is then converted and output as a low-noise electrical signal. 

 

Diagram of a bulk acoustic wave resonator. Image courtesy Texas Instruments.

 

BAW technology has been around for some time and has typically been used in very high-end, precise systems like radar, telecommunications, network equipment, and military applications. It has not been widely adopted because of its relatively high cost and larger size.

TI's BAW technology addresses these concerns, changing the scale at which BAW can be implemented. Upton notes, "We've taken this super high-performance technology and we're building it in a standard semiconductor process. We're bringing it down to devices that are used across a broad range of application, versus what has historically been these very niche, ultra-high-performance applications."

TI has released two devices to leverage the benefits of BAW.

 

Simplelink CC2652RB: The Industry's First Crystal-less Wireless MCU

TI has integrated their proprietary BAW clocking source into their existing 2.4 Ghz multi-protocol wireless MCU, the SimpleLink CC2652. It contains an ARM Cortex M4 microcontroller, a separate RF core with its own network processor. With analog peripherals, sensor interface, and embedded flash, it operates as a full SoC. 

 

The SimpleLink CC2652RB. Image courtesy Texas Instruments.

 

This integration eliminates the need for an external crystal. Building the BAW technology into the standard semiconductor manufacturing process allows TI to produce its enhanced MCU at high volumes.

By removing the crystal clocking device, the CC2652 saves a little over 12% of space on the PCB. The BAW technology reportedly brings performance advantages as well, with a more robust and stable clocking signal and a frequency stability of +/- 40ppm.

 

The crystal-less design of the BAW-integrated CC2652RB offers space savings on the PCB. Image courtesy Texas Instruments.

 

A battery sensor inside the device monitors power and temperature and provides active compensation, allowing the device to operate beyond the smaller temperature window of a typical quartz crystal application.

 

LMK05318 Network Synchronizer

The BAW resonator technology within the LMK055318 enables it to operate at a 400-Gbps link, well above the 100-Gbps rate effective today. It functions as a clock generator, jitter cleaner, and clock synchronizer in one device.  

 

The LMK05318. Image courtesy Texas Instruments.

 

In addition, BAW allows the LMK05318 to bring several additional performance increases to the market. The jitter performance measures 50-fs RMS at 312.5 MHz, while hitless switching is measured at +/-50-ps Phase Transient, both measures of higher performance being achieved with no additional components on the board, reducing the BOM.

 

Graph showing difference in phase noise with BAW technology. Image courtesy Texas Instruments

 

Since the integration of BAW grants more immunity to shock and vibration and eliminates certain EMI vulnerabilities, the LMK05318 displays much greater immunity to interference. Further, the reduced BOM and fewer external components make for a simplified circuit that improves performance further. 

 

Use Cases

TI feels these products represent step improvements in performance for both the MCU and clocking devices. They also bring BAW technology into a much wider range of use case possibilities, as their proprietary technology has made BAW smaller and more affordable. 

 

Large-scale Industrial Monitoring

Upton proposes a harsh scenario to display the capabilities of both devices. Deployed as part of a sensor inside a pump in a factory, the CC2652RB would face a difficult environment with vibration, motion, and moisture, and the sensor needs to run on very low power so that batteries don't need to be replaced often.

The CC2652RB's robust build would be able to handle this environment and provide consistent data, such as predictive maintenance, to keep the pump working and maintain factory uptime.

If there were many of these sensors deployed in pumps across a factory or industrial complex, they would produce a massive amount of data. The LMK05318 would be able to build cleaner signals and move that data in order to monitor all devices and maintain system-wide uptime.

 

Consistent Signal and Security

The lack of a crystal and the active temperature compensation make many other use cases applicable today. Upton mentions BLE applications that are susceptible to shock and vibration, or a smart home wireless base station that has its signal disrupted by vibrations from a truck passing by. The inherent robustness of the BAW technology makes the sigal stable in these scenarios. 

Further, the devices can be deployed in a wider range of temperatures with the active compensation. "If the environment changes, it's going to continue to compensate and work every bit as reliably as it did from the minute it was installed," notes Upton.  

Clock tampering is also more difficult with the BAW-based technology, as the signal remains steady and maintains uptime.

 

Other Possibilities

"This BAW technology has the potential to drive lots of advancements across a very wide-ranging set of applications," Upton states. "We're excited about the differentiation with BAW, and we're more excited about being able to apply that to real-world problems and looking forward to seeing what our customers will do with the technology."

 


 

Do you have experience with BAW? What possible uses do you see for this technology? Let us know in the comments.

 

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