
TI Claims Breakthrough in BAW On-Die-Oscillators - baybal2
https://www.eetimes.com/document.asp?doc_id=1334373
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ChuckMcM
This is a pretty big change for digital design. With high accuracy 48MHz
clocks on chip, parts that do USB become that much cheaper and more reliable.
Single chip USB-3.1 chips become possible as well.

The low phase noise is something that makes them very useful for wireless
systems that are all software radios these days anyway. Phase noise, or clock
jitter, results in difficulty in receiving closely spaced signals. And since
many (if not most) of the modern wireless protocols today are multi-channel,
it means you can make wireless protocols that support more clients in the same
spectrum, or more data to clients in the same spectrum.

I am hoping that as a minimum TI releases a series of 4 pin oscillators to
replace the ones like from Vectron that can be very finicky to keep working
precisely.

The only thing I didn't see was what is their vibration resistance standard?
The small 'can' oscillators can be pushed of their center frequency by yelling
at them ;-) It is a really hard problem to both secure a quartz crystal from
outside vibration influences and still allow it to vibrate at its intended
frequency!

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gugagore
I think it's so interesting that the best oscillators we can use in electronic
circuits, atomic clocks excluded, all operate in the mechanical domain. If I
knew nothing, I would assume we could build good RC oscillators, which are
purely electrical.

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ajross
What does "purely electrical" mean at this scale? Quartz resonators are piezo
_electric_ devices, after all. The same field of solid state physics that
explains a MOSFET is required to explain a oscillator.

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SamReidHughes
Quartz resonators still move and are affected by the direction of gravity

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gugagore
Yes! Here's a video:
[https://www.youtube.com/watch?v=zILwgQhjC_Q](https://www.youtube.com/watch?v=zILwgQhjC_Q)

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retSava
At a "couple of hundred microamps" penalty, this more or less kills a wide
range of potential products, ie battery-operated products like smart sensors
or remote controls and the like.

One of the most important factors for a long lifetime is to minimize the
static power draw, and running at 0.1--10 uA is quite common.

A common CR2032 has about 225mAh. If you can get 80% out of it, you have about
225 * 1000 * 0,80 / 24 = 7500,0 uA-days. At 10uA, you have roughly 2 years
(depending on usage etc). At "a couple hundred uA", you'll have two months.

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pplonbaw
I, too, chuckled at the "couple of hundred microamps" quote. However he refers
to the high-speed clock, which is turned on only during transmit/receive, and
is indeed negligible compared to the total power consumption during RF
communication.

That being said, their low-frequency on-chip oscillator specs are horrendous
(50ppm PER DEGREE). You can't maintain a BTLE connection or mesh node with
that kind of clock, you still need a 32kHz crystal oscillator, so TI haven't
"solved" the crystal oscillator problem just yet...

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zbrozek
Indeed; they clearly haven't solved accuracy. But they've done a remarkable
job of cleanliness. In particular, the close-in phase noise (e.g., at offsets
from carrier < 1 KHz) these BAW-endowed parts are _amazing_.

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ohazi
How does it fare in a slightly-helium-rich environment? That story about every
iPhone in a hospital shutting down for a week after an MRI shutdown turned out
to be due to not-quite-hermetically sealed packaging of the silicon mems
resonators.

~~~
baybal2
Ceramic piezo oscillators and silicon mems oscillators are a very different
technology based on different physics.

What matters here is the speed of sound in that ceramic piezo material. Can
helium change that by much? I don't know.

~~~
ohazi
...Yes? That's why I asked.

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cedivad
This is so funny to me. I instantly thought of the CC26xx series (FSK
transceivers) from TI when I first read the title, "Surely the next version of
their chips will use this amazing new tech and destroy the need for that
external epson oscillator!".

Sure enough, that's the first chip quoted in the article. That explains how
the newest CC2652 has been available in sampling quantities only for what, a
year now?

GG, TI.

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femto
Weird, the LMK05318 datasheet shows an external crystal oscillator on pins 31
and 32. Is this an older part and the integrated oscillator is not yet
released?

I went looking for phase noise specifications, as the article and CC2652RB
data doesn't have much to say about how the phase noise of the integrated
oscillator compares to an external oscillator.

[http://www.ti.com/lit/ds/symlink/lmk05318.pdf](http://www.ti.com/lit/ds/symlink/lmk05318.pdf)

[http://www.ti.com/product/LMK05318](http://www.ti.com/product/LMK05318)

~~~
zbrozek
In that particular part the BAW is part of a secondary, faster oscillator.
It's leveraged for its spectral purity - its phase noise - rather than its
accuracy. The datasheet you linked is for a clock chip that's designed to take
in a reference clock and transform it into multiple end-use clocks.

A really neat thing you can do with that part is use a GPS receiver's pulse-
per-second output as a high-accuracy, high-noise reference to generate high-
accuracy, low-noise, high-frequency clocks. It's something you would see in
datacenters or cell sites or distributed sensing systems.

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bgorman
Will this technology slowly replace external crystals for generic
microcontrollers? Or just for high-accuracy applications.

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dbcurtis
If it is as good as the article claims, I would say more like “instantly”.

Bringing the resonator on die eliminates the crystal from the BOM, one of the
pricier passive components. Also probably two capacitors are now gone, again
for xtal circuits you need better caps, cheapies are not good for oscillator
circuits. Plus the PCB area for the oscillator is eliminated, and that is an
area of PCB that requires careful layout to meet the constraints on paracitic
capacitance, etc.

~~~
janekm
Of course currently only TI can make these (though no doubt everyone else is
going to make a real effort to replicate). The chip in question is rather
pricey though, $11.44 in thousand quantities vs. $3.54 for the very similar
NRF52840 + about $1 for the crystal and other components needed.

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teraflop
You're looking at the price of their 400Gbps network synchronizer chip. The
other chip they mentioned with this technology, the wireless microcontroller,
is only $3.55.

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w0mbat
I assume this is the technology Apple is already using in their custom
silicon, and why there was that fairly recent story of a hospital where Apple
devices failed in the presence of helium leaked from their MRI installation.

~~~
ohazi
Apple is/was using silicon mems resonators, which is basically a fancy tuning
fork on flexures cut out of silicon. This technology ("bulk acoustic wave")
sounds like surface acoustic wave, but perhaps with the vibration mode being
through the bulk material rather than just the surface.

~~~
makomk
It also seems to fill a different niche from the MEMS resonators Apple are
using. Those are ultra-low-power 32KHz oscillators for keeping time in standby
mode, but the CC2652RB still relies on an external quartz crystal for that,
perhaps because this tech is even more power-hungry than the already too
power-hungry high frequency quartz oscillator it replaces.

~~~
abainbridge
Sounds like it is slightly higher power. From the article:

> Asked if there is any tradeoff by integrating a BAW resonator in the
> wireless MCU package, Wong noted a potential power delta at about 2% — “a
> couple of hundred microamps.” He called it “a reasonable tradeoff,
> [considering] its benefits outweigh [it].”

But, I guess if you can invest the money and area you saved by not having an
external crystal and buy a 2% bigger battery, which is probably a net win.

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m3kw9
The thing preventing this to be a home run is the power usage increase. +2% vs

