LT1034 burried zener - Page 1
Forum section: electronics / general

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 02, 2017, 06:33:39 pm
content: hello friends,i was wondering if anybody had had any experience with using LT1034 burried zener (7V) andits stability / noise characteristics?regards.

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: November 02, 2017, 09:16:33 pm
content: But its a bandgap reference, right?

author: BNElecEng
author_rank: Regular Contributor
timestamp: November 02, 2017, 09:31:11 pm
content: It's both. Check the lower half of that article. It seems there's a 7v buried zener as well as a band gap reference.I wonder what they had in mind when designing this particular reference?

author: Gyro
author_rank: Super Contributor
timestamp: November 02, 2017, 09:33:19 pm
content: Yes it has a burried zener but two issues that I can see...- No on-chip temperature sensor (unless you can use the bandgap ref in some way - unlikely).- The hermetic package is obsolete.

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: November 02, 2017, 09:40:43 pm
content: Yes, my bad. The datasheet is very confusing.Do the ppm and noise specs, for example, apply to the 2.5v part, the 7v piece, or both??Too, the description says that the 7v zener is for "less demanding" applications. What does that mean?

author: BNElecEng
author_rank: Regular Contributor
timestamp: November 02, 2017, 09:54:35 pm
content: In review, my response was harsher than I intended, sorry about that.I've taken a look at the data sheet and the noise figures seem to be for the band gap reference. There's very little info on the zener, apart from tempco and long term stability.

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 02, 2017, 10:23:23 pm
content: the question would be:-can you make a composite ref by thermally coupling lt1034 buried zener, and a (dual)transistor,into a ref-amp like assembly? (like sza263/ltflu) or further coupling a heater resistor to an ltz1000like assembly?as always, comments shall be highly appreciated.

author: Gyro
author_rank: Super Contributor
timestamp: November 02, 2017, 11:01:13 pm
content: Maybe, but thermal coupling to an epoxy package would be more difficult than a metal one. Also, a non-hermetic package probably isn't worth the effort (compared to an LM399 or a AD587UQ for instance) because it will be sensitive to both humidity and stress.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: November 02, 2017, 11:05:05 pm
content: How about something like the MAT01? Hermetic and they are matched.

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 02, 2017, 11:12:09 pm
content: Quote from: Gyro on November 02, 2017, 11:01:13 pmtrue, but having a buried zener accessible just like the ltz1000, makes the noise performance of the zener tunable by changing the current.anyways, before going into any thing else, the zener should be characterized for tempco and noise. we do have the long-term stability ca. 20ppm/rtKhr.regards.

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 08:23:25 am
content: Quote from: Gyro on November 02, 2017, 09:33:19 pmhello,how about using the bandgap in *forward* mode? (have a look at forward characteristics in the datasheet)regards.

author: BNElecEng
author_rank: Regular Contributor
timestamp: November 03, 2017, 09:48:18 am
content: Hi zhtoor,I think I'm missing something. The datasheet values and graphs don't show temperature dependence. Also, note 2 makes a statement that using either diode in forward mode will affect the operation of the other.

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 10:03:49 am
content: Quote from: BNElecEng on November 03, 2017, 09:48:18 amcorrect. the datasheet says so, i dont have access to physical samples yet, i suspect it is like the substrate diode in lm399 heater/ref.moreover, the bandgap reference can also be used as it is as a temperature sensor at least for the temperature rangesca. 0-50 degC (+24ppm/degC) and 75-125 degC (-24ppm/degC) according to the "temperature drift" of the band-gap portion. the area between 50-75 degC is probably too little slope for temperature measurement of the die.btw, does anybody have access to an older datasheet, maybe detailing the internal circuit diagram?thanks and regards.

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 17, 2017, 01:48:10 am
content: hello friends,has anybody measured the tempco of the auxilliary burried zener in LT1034,is it in the region of ca +2mv / degC ?regards.

author: bopcph
author_rank: Contributor
timestamp: November 20, 2017, 02:46:59 pm
content: Quote from: zhtoor on November 17, 2017, 01:48:10 am40ppm/deg.C = 0.28mV/deg.C (7V) @ 100uA !!, no sign on the 40ppm so can we expect that to be positive ppm's ?But what TC to expect at 1mA or 5mA ??No noise specs !, 20ppm/khr !It will have to be Real cheap if its to be worth using your sparetime onI would rather bet on a well spec'ed buried zener in a hermetic ceramic house or metal-can and use my time on building a well controlled oven and stable current source

author: zhtoor
author_rank: Frequent Contributor
timestamp: November 20, 2017, 03:04:44 pm
content: Quote from: bopcph on November 20, 2017, 02:46:59 pmthanks.your data matches well with diligentminds.com(ken) statement of around 17% of -2.1mv/degC of Vbe tempco.the next step should be noise characterization vs current on this (probably *only* accessible burried zener besides LTZ1000)and if the noise levels are interesting (say sub 1ppm) then compensation strategy with a scaled down Vbe of a thermallycoupled transistor.as far as the cost: LT1034CZ-2.5 USD 2.5/Qty=1 and USD 2.15/Qty=100(you are interested *only* in the *auxilliary* zener)composite:couple LT1034 (TO-92) with flat side matching with 2N3904 (TO-92) leads opposite,wrap kapton tape over them, make a small nichrome wire heater over this assembly,wrap with kapton tape and thermally insulate, followed by heat-shrink tubing, and voila!*maybe* a synthetic LTZ1000(or LTFLU/SZA263) look-alike.as far as hermetic sealing goes, maybe dip the whole shebang into a molten pool of solder-glass.(parylene maybe for the RICH MAN)still waiting for my samplesregards.-zia