[HN Gopher] Analog Devices AD1139
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Analog Devices AD1139
Author : picture
Score : 96 points
Date : 2021-11-20 07:03 UTC (15 hours ago)
(HTM) web link (www.richis-lab.de)
(TXT) w3m dump (www.richis-lab.de)
| sneeeeeed wrote:
| Great tear down but I'm more of a TDA1541 man myself.
| th0ma5 wrote:
| Really nice tear down. These digital synthesizers have been
| really great for breathing new life into amateur radio and
| digital single generation.
| londons_explore wrote:
| Are the traces gold plated?
| jjoonathan wrote:
| Yep. This hybrid was probably manufactured in open air, so they
| would want gold plating to prevent it from oxidizing while
| heated during wirebonding / die attach.
| desdiv wrote:
| Some context:
|
| >The AD1139 is the first DAC offering 18-bit resolution (1 part
| in 262,1441) and true 18-bit accuracy in a component size hybrid
| package. A proprietary bit switching technique provides high
| accuracy, speed and stability without compromising small size or
| low cost.[0]
|
| Just curious, I looked up the price:
|
| Digikey, 1 unit: $2,449.80 USD [1]
|
| Analog Devices, 100-499 units: $1706.58 USD
|
| Analog Devices, 1000+ units: $1706.58 USD
|
| [0]: https://www.analog.com/en/products/ad1139.html
|
| [1]: https://www.digikey.com/en/products/detail/analog-devices-
| in...
| metafex wrote:
| that's interesting, ADI doesn't even list it anymore on their
| website but it's marked as still active. i guess it's still
| used in some test&measurement equipment.
| the__alchemist wrote:
| There seems to be no price cap on AD components! Solid stuff at
| a range of prices. It's sometimes tough to tell what makes the
| super-expensive ones different. Might be a little extra
| precision (etc) that's justified in niche cases.
| MisterTea wrote:
| I'd say volume. These are highly specialized devices which
| require a lot of careful development. The volume might be a
| few thousand a year if even. So seeing super high
| speed/precision ADC's costing 1000+USD isn't so surprising.
| jeffbee wrote:
| Isn't is just market segmentation? The only people who need
| this thing are building test equipment that costs big money
| regardless.
| coretx wrote:
| I'd love to have one in my radio
| GeorgeTirebiter wrote:
| How could one use an 18-bit D/A in a radio? (an 18-bit
| A/D is a different story).
| madengr wrote:
| I suppose if you were doing some PA linearization
| techniques (e.g. digital predistortion), one could use
| that dynamic range.
| jareklupinski wrote:
| this feels like something to throw into a satellite for
| processing/digitizing the output from a custom image sensor?
|
| or maybe some incredibly edge software-defined radio
| application...
| Pixelbrick wrote:
| Great write up - thanks OP, I'd not seen a hybrid torn down like
| that before.
| aix1 wrote:
| Beautiful pics. I wonder why, in a few places, there are _pairs_
| of bonding wires connecting the same pads.
| magicalhippo wrote:
| > Beautiful pics.
|
| He uses[1] Helicon Focus[2] for focus stacking.
|
| A lot of these die shots are pieces of art, and also quite
| interesting. I especially like the LTZ1000 voltage reference[3]
| or the Thyracont Inclinos[4] which is an accelerometer without
| moving parts. A lot of the MEMS dies are also very interesting,
| because of their moving parts, like this[5] ADXL213.
|
| [1]: https://www.eevblog.com/forum/projects/transistors-die-
| pictu...
|
| [2]: https://www.heliconsoft.com/heliconsoft-products/helicon-
| foc...
|
| [3]: https://www.richis-lab.de/REF03.htm
|
| [4]: https://www.richis-lab.de/MEMS_04.htm
|
| [5]: https://www.richis-lab.de/ADXL213.htm
| FPGAhacker wrote:
| I'm speculating but when I've seen it in the past it was for
| handling higher current.
|
| In this case I'm wondering if it's used to maintain better
| control of the voltage gradient on a pad.
| ejiblabahaba wrote:
| Sometimes it's to handle higher currents, other times it's to
| reduce the bond wire inductance and improve the high-
| frequency response. For power pins it can be both. Especially
| for a multi-chip module with some digital circuitry, there's
| potential for high-frequency digital transients that need
| nearby decoupling capacitors through low-inductance loops, or
| the transistor switching noise can pollute other copackaged
| circuit supplies; amplifiers also benefit from lower
| inductance on the supply lines since it stabilizes the
| frequency response at higher offsets beyond the loop
| bandwidth of any integrated supply regulation, current
| sources, bandgap references etc. So you're essentially
| correct, it's about voltage gradients, but probably at higher
| frequency.
| loxias wrote:
| Really stupid question: I thought I've used a 24bit DAC, on some
| high end sound equipment. Why is this special/noteworthy?
| jeffbee wrote:
| I doubt anyone ever shipped this DAC for digital audio
| applications. You're right that on sheer width there have been
| 18-bit or better DACs on the market since the 1980s. First one
| that comes to mind is the Burr-Brown (now Texas Instruments)
| PCM58. ADI themselves have been marketing 18-bit or better
| audio DACs for ages, since at least the AD1860. Compare the
| datasheet of the AD1860 to this one to see the difference
| between a precision DC instrument and a dynamic audio DAC. This
| one has .01% gain error while an audio DAC is rated for 2% gain
| error (because nobody cares).
| intricatedetail wrote:
| These industrial DACs are actually brilliant for audio - They
| retain low-end and transients much better, but it also means
| need to be calibrated properly so that DC don't destroy
| speakers. It's easier and cheaper to just add HPF though, but
| sounds "worse".
| makomk wrote:
| Most "24 bit" audio DACs have a lot less than 24 bits of real
| usable data due to the noise floor effectively burying the
| lowest bits in garbage, and I think the noise increases at less
| perceptually noticable frequencies too. 24 bits is used for
| audio mainly because it's just convenient to standardise on
| that. I think they also have a lot more non-ideal behaviour in
| general than this, and they certainly don't have a 0.1%
| precision voltage reference because the precise output voltage
| range doesn't really matter for audio.
| VLM wrote:
| You can specify 144 dB of dynamic range but in practice:
|
| 1) Loudness war means pro sound engineers will mix everything
| to be full scale all the time so music has 0 dB of dynamic
| range ideally
|
| 2) Almost no one owns equipment capable of rendering 144 dB of
| dynamic range even if they have a bit stream specifying it. So
| if a quiet near silent room is 30 dBA where you hear your own
| heartbeat and OSHA permissible exposure limit is 90 dBA its
| only 60 dB of dynamic range between "too quiet to hear" and "so
| loud you legally need earplugs" so you'll be throwing out about
| 84 dB of theoretical dynamic range anyway even if you owned
| gear capable of rendering it. Note that its very hard to buy
| audio amplifiers capable of more than 90 dB or so SNR even if
| just hooked up to test equipment, nothing on the market capable
| of 144 dB, so either the bottom end will be lost in the hiss or
| the high end will be distorted into unrecognizability.
|
| 3) Then you get into topics like power supply rejection ratio.
| A "bad" amp would pass noise from the power supply thru. A
| "better" amp rejects more noise from the power supply. A good
| way to look at it is the hummmmm and crackle and stuff that you
| hear on a bad old tube amp could be modeled as a very large
| value attenuator directly connecting the power supply to the
| output. With 1970s tech and capacitors, 80 dB was considered
| pretty good PSRR. The very top end newest class D amps can just
| barely exceed 100 dB PSRR under idealized testing conditions.
| So at full blast (which would just blow your eardrums out
| anyway) everything more than 100 dB down from peak will merely
| be power supply noise passed thru the system.
|
| Its kind of like I can spec a piece of wood to 1.5875mm thick.
| And then convert it to imperial inch measurements. If the best
| measurement tool I have to measure wood, is a carpenters tape
| measure ruled to eighths of inches, the best measurement I can
| do to render those five digits of precision is "about half a
| division" on that tape measure. The five digits of precision in
| the mm figure imply I should be using a calibrated micrometer
| to measure that thickness, but if you assume technology hasn't
| invented them yet, then there's little point in spec a digital
| calculated measurement to five digits of mm precision. Likewise
| I can make a string of binary 1 and 0 that theoretically can be
| understood or mathematically proven to imply 144 dB of sound
| precision, but even in 2021 electronics hardware doesn't exist
| to reliably repeatedly and provably render those 1 and 0 into
| sound, at least not at audio rates.
|
| Note that 2 to the power of 24 is a eight digit number,
| implying you're operating at tens of ppb. NIST has really nice
| new Josephson junction standards capable of reliably operating
| at tenths of ppb. So you're very optimistically trying to field
| gear operating at only a hundred times less accurate than the
| best lab in the entire world can currently measure. Good luck
| with that. That's why nobody sells voltmeters with more than 8
| or so digits of precision, if the world standard calibration
| system only has ten digits on its best days, no point building
| voltmeter hardware displaying 12 or 15 digits LOL. We don't
| really have the technology to do 24 bit accurate voltages out
| in the field right now. So if we can't build or calibrate
| testing gear significantly better than 24 bits, like to 32 or
| so bits perhaps, there's no way to actually measure and tell if
| 24 bit gear is accurately precisely repeatedly working to 24
| actual bits of precision. Maybe your audio gear is distorting
| in a subtle fashion and only operating to 22 noise free bit and
| the last two bits are essentially a RNG or stuck on/off or
| otherwise no relationship with reality; very few electronics
| labs in the entire world have the gear to prove that claim true
| or false.
| magicalhippo wrote:
| Not all DACs are equal.
|
| Even average soundcards sport a 24bit DAC. However they're
| designed for a dynamic output so tend to have quite crap DC
| precision. What matters to a soundcard is producing a precise
| waveform, not a precise DC voltage.
|
| This part is designed for DC level setting, ie a programmable
| reference voltage. Typically it won't change that often
| (compared to a soundcard), but it needs to be precise.
|
| For example, compare the AD5791[1], a 20-bit DAC with 1LSB DC
| accuracy costing $40 in 1000 qty, to a 24bit audio DAC like the
| AD1955[2] costing about $7. The datasheet for the audio DAC
| doesn't even specify the DC precision, only a 6% gain error
| from the output buffer.
|
| [1]: https://www.analog.com/en/products/ad5791.html
|
| [2]: https://www.analog.com/en/products/ad1955.html
| mastax wrote:
| On the other hand if all you care about is DC precision you
| can use a very simple, though not necessarily easy, circuit.
| You need a stable voltage derived from a stable voltage
| reference, and a stable clock to PWM that stable voltage.
| Then you "just" low-pass filter the heck out of the PWM to
| get an adjustable DC value, and calibrate out any offsets.
| I've seen this used in adjustable voltage standards (forget
| which) and the venerable Fluke 5700A Multifunction
| Calibrator[0].
|
| [0]: https://www.youtube.com/watch?v=qhr6h7wuqo0
| LeoPanthera wrote:
| I believe this chip was first available in 1989. It's old
| technology.
| loxias wrote:
| Ahh, so this is a "remember this?" post. Got it. Thanks :)
| sitkack wrote:
| old technology is not bad technology.
| londons_explore wrote:
| When was this released?
| Renaud wrote:
| Looks like it's as least as old as the 90s. Found a picture of
| one sporting a 9943 date code. The one in the article is from
| 2002.
|
| Analog still lists them in production!
| tpmx wrote:
| The datasheet PDF doesn't contain an obvious date, but it's
| is clearly scanned and it also contains a sample circuit for
| connecting it to an IBM PC via the ISA bus. So somewhere
| between 1981 and 1995, perhaps.
|
| There's a document id on the last page that may indicate it's
| from 89.
|
| https://www.analog.com/media/en/technical-
| documentation/data...
| sydthrowaway wrote:
| AD make some good chips. Along with Realtek they kickstarted the
| SDR revolution. No hype or trite SaaS products here, just good
| old school engineering.
|
| If only they paid like they sold ads.
| analog31 wrote:
| I work in mostly "hardware" development. Long ago I made peace
| with the fact that there would always professions that pay more
| than mine, for doing things that I can't comprehend.
| madengr wrote:
| Ha ha, and you are doing things for less that they can't
| comprehend. Oh well, RF EE myself.
| artemonster wrote:
| it annoys me to an unbelievable levels that all that CRUD SaaS
| crap is called "tech" nowadays.
| anthomtb wrote:
| It's annoying for sure. But, in fairness to those SAAS apps,
| "tech", as recognized by the mass audience, is short for
| information technology. Meaning conveying knowledge to
| another person as efficiently as possible. So that lame-
| sounding SAAS app might really be a small leap forward in
| transfer of knowledge. Even if the underlying implementation
| is something a high school student could figure out.
| auxym wrote:
| We're veering pretty far off-topic, but, as a mechanical
| engineer working in research, yes.
|
| Develop a new ceramic material for advanced turbofan engines?
| Not tech.
|
| Web front end? Oh yeah, tech.
| omneity wrote:
| Isn't that just called engineering?
| jhgb wrote:
| No, technology is the application of science and other
| knowledge to achieve practical goals. It started with
| agriculture, metallurgy, etc. thousands of years ago.
| loxias wrote:
| But think of the epic problems they needed to solve to get
| the protocol implemented using websockets in javascript so it
| can run in the iframe on the mobile browsers! Such
| engineering prowess! </sarcastic>
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(page generated 2021-11-20 23:02 UTC)