Which voltage has the lowest average temperature coefficient (say 20C to +40C): 4.7V or 5.1V? "Average" is to mean a sample of 150 from hundreds of thousands.
Is there a variation of the average TC between parts from wafer to wafer, and how much?
Ref: Vishay MMBZ230, MMBZ5231.
IIRC traditionally that is 6.2V or 6.8V. Check the datasheet to make sure.
-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
0C
from what I've read zero is supposed to be around 5V
the slightly higher voltages might be a zener and diode in series so the positive and negative coefficient balance out
-Lasse
ON the very first day of my very first engineering job, my mentor took me aside and informed me that I could trust what it said on the data sheet some of the time. Selected parts were a no-no.
I once had to clean up after an engineer who'd used a selected part. It was part numbered. There were a kagillion of 'em in stock. And it was dirt cheap compared to the alternatives.
Nobody bothered to check and learn that the project that had specified the part had bought a lifetime supply and that the company was out of business. We learned the hard way when both production lines shut down.
I think you're mixing standard versus compensated.
Thinking back to my days at Dickson Electronics, I made hybrid circuits, the other half of the building made TC'd zeners... if I'm remembering correctly 5.6V + a diode drop = 6.2V, physically a chip-stack the way they made them, had virtually zero TC.
But I could be remembering wrong... that was 40 years ago :-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| 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.
I really like LM329s, but they don't come in SMT and there's some worry that they may go away. I usually put in a population option, so that the 329 can be replaced with something like an LT1021-7. Those are a lot more money, and no better for most of my uses, but if the 329 goes away, no board spin is required.
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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Just also remembering that, on a single bipolar process, that 5.6V + TWO Vbe's, made a nearly flat 7V.... that's what is in most of my alternator regulator patents. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| 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.
Depends on the operating current. 5.6 may be better.
Use a bandgap!
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Why not use an LM4040/4041 or some such?
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
20C
Motorola made a lot of money selling the the 1N823 - 1N829 series
which is a 5.6V zener in series with a regular diode.
5.6V is far enough out of the Zener breakdown region and close enough to the avalanche region that positive temperature coefficient of the Zener diode was as predictable and stable as the negative temperature coefficient of the forward drop across the regular diode.If they could have done as well with a 5.1V zener on its own, I don't think that they would have bothered inventing the 1N823 series.
-- Bill Sloman, Nijmegen
-- http://www.onsemi.com/pub_link/Collateral/HBD854-D.PDF Page 30
MANY years ago I did this exercise with through-hole zeners and came up with a 1N751A (5.1V nominal) at some particular operating current (can't remember now, but NOT particularly low).
You'd be better off using the cheapest regulator you can find- most of them use bandgap references internally, even if they don't advertise it. Or a shunt reference like a TL431.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Buried zeners generally have much better noise and long term stability than bandgaps, AFAIK. So that could be it.
-- John Devereux
There's also those floating gate types, if that concept doesn't keep you awake at night.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
(a) Bandgaps are a good 20 dB noisier than buried zeners. The LM4040's
1-Hz noise is over 1 uV in the flatband when scaled to 7V, whereas the LM329's is 70 nV (23 dB lower). Also the 1/f noise corners are about the same, say 12 Hz, but the LM4040's 1/f noise is thus also >20 dB worse.(b) The 4040's initial accuracy is good, but its tempco is poor. TI doesn't make the good grade of LM329 anymore, but they're generally much better than the quoted typical 50 ppm/K. LTC still makes the good ones for occasions when that matters (6 ppm typical).
(c) I prefer through-hole for voltage references because it reduces die stress, which can make the voltage walk all over the place. Routing a C shape in the board around the reference works OK too, or so I'm told.
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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
See e.g. AN82 page 7
-- John Devereux
to
Yeah, like that. Getting good low-frequency stability from a reference can be a challenge. I usually don't care that much about absolute accuracy, but some folks use my gizmos to make measurements lasting many hours, so stability is really important.
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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
We like ADR420-series (jfet things) parts for serious references. The B grade is 1 ppm/degC typ. But we are more concerned with TC and stability than noise, although their noise is pretty good too.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
to
Those are pretty nice parts, but I bet they don't cost $0.30 like an LM329! ;)
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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
20C to o .
ry
at
a s s s CI'm going with the LTC6655-5 in my low distortion oscillator. I was thinking of the Analog Devices jFET things, but one of my Dutch contacts had had trouble with bad 1/f noise, and recommended the LTC6655 as a whole lot better.
-- Bill Sloman, Nijmegen
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