I was very happy to see Texas Instruments (TI) recently enter the Bulk Acoustic Wave (BAW) resonator realm. This effort is critical to the efficient movement and analysis of large amounts of data. With the addition of a connected MCU, TI now has a really neat dynamic duo solution that will enable a new level of performance in technology.
What is BAW?
BAW technology is essentially a tiny micro-resonator technology which allows for designers to integrate clocks, that are high-precision and ultra-low jitter, into packages with additional circuitry; this architecture is fabricated in Silicon. The alternative solution is external Quartz crystal designs, which are physically larger. This clock integration is an increased barrier to clock tampering.
Letís first look at what limitations there are in todayís design architectures with clocking and Quartz crystal devices and how BAW devices will enhance these systems in performance. cost, and size. See Figure 1 for the size advantages of BAW vs. Quartz crystal oscillators.
Employing TIís CC2652RB, a multi-standard MCU with on-board BAW clocking architecture in a single package (Image courtesy of Texas Instruments)
The CC2652 is a fully integrated wireless MCU that has been in production for a while. It is an applications MCU coupled with a highly integrated radio and network processor for 2.4 GHz. The new solution, CC2652RB, has an integrated BAW device inside the package with the MCU. TI claims that this is the first MCU without a crystal. Designers will love this BAW integration because external crystals plague designers with placement, routing, size, temperature, vibration (many external wireless transceivers in 5G systems will be deployed on outdoor light poles, buildings, and other outdoor areas where such things like truck vibrations will cause oscillator errors to sensitive Quartz crystals), and compensation and with this level of integration, designers one less thing to worry about regarding the details of routing and placement of an external oscillator.
The BAW device has +/- 40ppm frequency stability across the full operating temperature range, by internal active compensation via taking readings on the BAW over temperature and power. All this in a 7x7 mm QFN package.
BAW Network Synchronizer
The other device in this duo is the LMK05318, a network synchronizer, with a BAW-based resonator that enables 400 Gbps links at low jitter, without any additional external components. See this white paper, TI BAW technology enables ultra-low jitter clocks for high-speed networks, for more technical details.
The network synchronizer takes the network clock and cleans it to power the data converters, FPGAs, and other analog components downstream. TI claims that this is the first Network Synchronizer with an integrated BAW device. This enables the 400 Gbps link requirement in the 5G ecosystem in a much easier manner. The link robustness and the ability to continuously maintain 400 Gbps is critical. If the clock source is not very clean, the 400 Gbps cannot be maintained and you may not even reach the 400 Gbps rate.
The jitter performance of 50 fs RMS at a clock output of 312.5 MHz (APLL1) and 125 fs RMS at 155.52 MHz (APLL2) without requiring any additional components. In these critical communication systems, reliability and redundancy are so important. If one clock fails, then they want to seamlessly transition to the next backup clock. That is why this synchronizer also has four times better hitless switching (+/- 50 ps Phase Transient) vs. the competition. You will not lose the frame synchronization.
Stability under vibration is especially important in automotive usage. This technology will be most important in that market.
As usual, TI always has excellent application notes to go along with these kinds of innovative new solutions:
ITU-T G.8262 compliance test results for the LMK05318
Supported synchronization modes for TI network synchronizers
Understanding clocking needs for high-speed 56G PAM-4 serial links
How to use the LMK05318 as a jitter cleaner
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For more information visit the Texas Instruments website