silicon oscillators

[John Larkin]

Has anyone used silicon oscillators? I'd like to stock a few SOT-23
oscillators to replace quartz crystal oscillators for non-critical
stuff. Something cheap, of course.


--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[Jim Thompson]

On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:

>Has anyone used silicon oscillators? I'd like to stock a few SOT-23
>oscillators to replace quartz crystal oscillators for non-critical
>stuff. Something cheap, of course.

I know that MicroChip has some semi-stable oscillators (I designed
some for them :-)

Whether they are available stand-alone, I don't know.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[John Larkin]

On Thu, 18 Sep 2014 13:43:29 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin
><jla...@highlandtechnology.com> wrote:
>
>>Has anyone used silicon oscillators? I'd like to stock a few SOT-23
>>oscillators to replace quartz crystal oscillators for non-critical
>>stuff. Something cheap, of course.
>
>I know that MicroChip has some semi-stable oscillators (I designed
>some for them :-)
>
>Whether they are available stand-alone, I don't know.
>
> ...Jim Thompson

LTC has nice stuff, but it costs as much as an XO.

The MEMS oscillators seem to be expensive, too.

A CMOS oscillator would be a tiny chip with three wire bonds. Why
wouldn't that cost 10 cents? OK, it's trimmed, so 11 cents.

[Jim Thompson]

On Thu, 18 Sep 2014 13:59:58 -0700, John Larkin

<jla...@highlandtechnology.com> wrote:

>On Thu, 18 Sep 2014 13:43:29 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin
>><jla...@highlandtechnology.com> wrote:
>>
>>>Has anyone used silicon oscillators? I'd like to stock a few SOT-23
>>>oscillators to replace quartz crystal oscillators for non-critical
>>>stuff. Something cheap, of course.
>>
>>I know that MicroChip has some semi-stable oscillators (I designed
>>some for them :-)
>>
>>Whether they are available stand-alone, I don't know.
>>
>> ...Jim Thompson
>
>LTC has nice stuff, but it costs as much as an XO.
>
>The MEMS oscillators seem to be expensive, too.
>
>A CMOS oscillator would be a tiny chip with three wire bonds. Why
>wouldn't that cost 10 cents? OK, it's trimmed, so 11 cents.

What kind of frequencies and stability are you looking for?

[Allan Herriman]

On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin wrote:

> Has anyone used silicon oscillators? I'd like to stock a few SOT-23
> oscillators to replace quartz crystal oscillators for non-critical
> stuff. Something cheap, of course.

Perhaps not what you're looking for, but I put a Silicon Labs Si5340 into
a product recently. It has a 14GHz internal VCO with four frac-N output
dividers, and a frac-N feedback divider that allows it to synthesise just
about any four frequencies up to 800MHz to better than 0.1ppm. If the
frequencies you want are integer numbers of Hz, it will synthesise them
with 0ppm error. At least it did that for all the test frequencies I
tried.
The frac-N dividers have dynamic phase adjusters to help reduce the
jitter due to the fractional N division process. They don't say how this
is done, but I assume that they get multiple phases from the 14GHz VCO
and switch between them.

It's programmable over I2C or SPI. It also has a one-time programmable
memory so you can get it to power up with the frequencies you want, but
I'm not using that in my application.

I used a 48MHz TXCO as the input reference.

The datasheet doesn't give phase noise plots. (The part is new. I
expect phase noise plots to turn up in future releases.)

I tried to measure the performance. I couldn't see any but the carrier
above the noise floor of my spectrum analyser at any span / rbw setting.
Ok, I need a better spectrum analyser.
With the four outputs set to different frequencies, I measured crosstalk
between adjacent outputs at about -80dB.

I don't have access to a phase noise test set any more so I can't do any
real phase noise measurements :(

On my trusty Agilent scope (20GSa/s, not sure of jitter spec), I measured
the relative jitter between the Si5340 outputs. This type of measurement
shows up the jitter from the output dividers but not the VCO.
At 600MHz, with all the test outputs at the same frequency I measured
about 30ps p-p on infinite persistence. I repeated the same test with
frequency offsets, e.g. output 1 was 600MHz, output 2 was 600.0000001MHz,
etc. causing the traces to drift slowly past each other on the scope.
The jitter seemed to be about 50ps p-p.


I think the performance is good enough for my needs. A decade back, that
sort of performance on four channels would have cost a few hundred
dollars [VCSOs, buffers, PLL per channel]. Now it's $20.

Regards,
Allan

[John Larkin]

On Thu, 18 Sep 2014 14:52:35 -0700, Jim Thompson

<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Thu, 18 Sep 2014 13:59:58 -0700, John Larkin
><jla...@highlandtechnology.com> wrote:
>
>>On Thu, 18 Sep 2014 13:43:29 -0700, Jim Thompson
>><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>
>>>On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin
>>><jla...@highlandtechnology.com> wrote:
>>>
>>>>Has anyone used silicon oscillators? I'd like to stock a few SOT-23
>>>>oscillators to replace quartz crystal oscillators for non-critical
>>>>stuff. Something cheap, of course.
>>>
>>>I know that MicroChip has some semi-stable oscillators (I designed
>>>some for them :-)
>>>
>>>Whether they are available stand-alone, I don't know.
>>>
>>> ...Jim Thompson
>>
>>LTC has nice stuff, but it costs as much as an XO.
>>
>>The MEMS oscillators seem to be expensive, too.
>>
>>A CMOS oscillator would be a tiny chip with three wire bonds. Why
>>wouldn't that cost 10 cents? OK, it's trimmed, so 11 cents.
>
>What kind of frequencies and stability are you looking for?
>
> ...Jim Thompson

10, 25, 100 MHz would be handy. 1% looks do-able in silicon
oscillators.

[MK]

I've been using the Silicon Laboratories parts (like 501BAA16M0000CAF)
but they cost about $0.70 @ 1k. Typical crystal oscillator type specs,
20ppm or 50ppm.
Where can you get a SOT23 part with a decent (ie better than 0.1%) spec
at anything near $0.10. I found some ST parts on Digikey at $0.26 on a
3k reel but they had no stock, 1.5% spec.

Michael Kellett

[David Brown]

I would imagine 1% would be easy at roughly room temperature, but you
could get a lot of temperature dependence for the frequency.

The built-in oscillators (which I /think/ are CMOS oscillators) in
Freescale Kinetis microcontrollers are around 0.1% at room temperature,
according to the samples I took. Since the cheapest of this chips is a
Cortex M0+ microcontroller at about 1mm x 2mm for less than 50 cents, I
would not expect a high price for a stand-alone oscillator.

[George Herold]

On Thursday, September 18, 2014 4:59:58 PM UTC-4, John Larkin wrote:
> On Thu, 18 Sep 2014 13:43:29 -0700, Jim Thompson
>
> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>
>
> >On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin
>
> ><jla...@highlandtechnology.com> wrote:
> >
> >>Has anyone used silicon oscillators? I'd like to stock a few SOT-23
> >>oscillators to replace quartz crystal oscillators for non-critical

<snip>

>
> LTC has nice stuff, but it costs as much as an XO.
>
> The MEMS oscillators seem to be expensive, too.
>
> A CMOS oscillator would be a tiny chip with three wire bonds. Why
> wouldn't that cost 10 cents? OK, it's trimmed, so 11 cents.
>

I'm confused about what you mean by a silicon oscillator. You mean some Schmidt trigger inverter and RC thing?

George H.

[John Larkin]

Exactly. We use NXP ARM chips that have excellent oscillators inside.

[John Larkin]

On Fri, 19 Sep 2014 06:08:11 -0700 (PDT), George Herold
<ghe...@teachspin.com> wrote:

>On Thursday, September 18, 2014 4:59:58 PM UTC-4, John Larkin wrote:
>> On Thu, 18 Sep 2014 13:43:29 -0700, Jim Thompson
>>
>> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>
>>
>>
>> >On Thu, 18 Sep 2014 13:13:53 -0700, John Larkin
>>
>> ><jla...@highlandtechnology.com> wrote:
>> >
>> >>Has anyone used silicon oscillators? I'd like to stock a few SOT-23
>> >>oscillators to replace quartz crystal oscillators for non-critical
><snip>
>>
>> LTC has nice stuff, but it costs as much as an XO.
>>
>> The MEMS oscillators seem to be expensive, too.
>>
>> A CMOS oscillator would be a tiny chip with three wire bonds. Why
>> wouldn't that cost 10 cents? OK, it's trimmed, so 11 cents.
>>
>I'm confused about what you mean by a silicon oscillator. You mean some Schmidt trigger inverter and RC thing?
>
>George H.

Well, a fancier version, more stable. They are inside lots of uP
chips, and LTC sells them as standalone oscillators, but they seem
expensive to me.

Looks like I can buy an ARM chip for 50 cents and use it just for the
oscillator inside... for 1/3 the price of an LTC oscillator.

[Phil Hobbs]

Are you talking about the micromachined silicon resonator MEMS
oscillators, or the tweaked ring oscillators of MCUs? Their jitter
behaviour is going to be pretty different, I expect.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

[John Larkin]

The "silicon oscillators" are just analog circuits, compensated RC
oscillators of some sort. Power consumption and TC are low, so they
are probably not ring oscillators, I'm guessing. Maybe an integrated
555 sort of thing? Silicon capacitors are excellent, and good current
sources can be done on-chip.

MEMS oscillators generally cost more than XOs!

[Tim Williams]

"George Herold" <ghe...@teachspin.com> wrote in message
news:8e31c614-61a4-4c38...@googlegroups.com...

> I'm confused about what you mean by a silicon oscillator. You mean some
> Schmidt trigger inverter and RC thing?
>

AFAIK, there are two main types: LC and MEMS.

In the former case, a shielding can is formed by tracks and vias in every
metallization layer, then planar structures such as spiral inductors,
transmission lines, etc. are fabricated inside. (The 'tub' structure may
not be strictly necessary, but silicon probably makes an awful ground
plane. RF chips incorporating tuners and amplifiers would still use
shielding for internal isolation though.)

Such inductors have ratty Q (peaking at 5-15 or so in the 4-20GHz range),
but they're good enough to make simple things with. So, add varactors and
compensation circuitry, and you've got a reasonably stable oscillator
(and, as it turns out, a pretty stable one in general).

The MEMS product uses electrostatic deflection on a tuning fork, or
something like that, which I presume has much better Q, and probably lower
operating frequency. I would think they're sensitive to rotation or
acceleration, but that's probably nulled out by design (whereas, MEMS
accelerometers optimize for the opposite effect..).

In either case, a DDS or whatever furnishes a programmable output
frequency. Such devices are often programmed by the supplier as Value-Add
parts.

Both components are comparable to crystal oscillators (which are arguably
MEMS devices as well, but not monolithic), though no one really talks
about the close-in versus far-out stability / jitter tradeoffs, if any.

Tim

--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

[Jim Thompson]

On Fri, 19 Sep 2014 16:55:51 -0500, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

>"George Herold" <ghe...@teachspin.com> wrote in message
>news:8e31c614-61a4-4c38...@googlegroups.com...
>> I'm confused about what you mean by a silicon oscillator. You mean some
>> Schmidt trigger inverter and RC thing?
>>
>
>AFAIK, there are two main types: LC and MEMS.
>

[snip]

Most are trimmed RC oscillators... with SiCr resistors and SiO2
capacitors the stability after trimming is quite respectable.

[Tim Williams]

"Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> wrote
in message news:v3ap1a5l4pu87crr0...@4ax.com...

> Most are trimmed RC oscillators... with SiCr resistors and SiO2
> capacitors the stability after trimming is quite respectable.

Really, I would've thought that too noisy; it's occasionally even
suggested as a TRNG source in MCUs (compare internal RC to external XTAL,
siphon off LSBs of frequency counting).

Or maybe that's just the shitty MCUs. :)

[rickman]

I'm surprised to hear you say that. Every time I've looked at them they
were very price competitive. I think they would not sell at all if they
weren't. It's not like they do much better than an XO in any way.

--

Rick

[rickman]

On 9/19/2014 7:05 PM, Tim Williams wrote:
> "Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> wrote
> in message news:v3ap1a5l4pu87crr0...@4ax.com...
>> Most are trimmed RC oscillators... with SiCr resistors and SiO2
>> capacitors the stability after trimming is quite respectable.
>
> Really, I would've thought that too noisy; it's occasionally even
> suggested as a TRNG source in MCUs (compare internal RC to external XTAL,
> siphon off LSBs of frequency counting).
>
> Or maybe that's just the shitty MCUs. :)

Everything according to the requirements. Many designs only need timing
accuracy good enough to run a UART. Why worry about 100 ppm timing when
you are operating a toothbrush, a microwave or many, many other devices.

Oh, I forgot about that special grade, there's A, B and "Shitty" in the
oscillator families.

--

Rick