High voltage reference in an original way :D - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: October 03, 2016, 04:59:49 pm
content: http://www.ti.com/lit/an/sbaa203/sbaa203.pdf

author: EmmanuelFaure
author_rank: Regular Contributor
timestamp: October 03, 2016, 05:20:16 pm
content: Original, or pure stupid?

author: JS
author_rank: Frequent Contributor
timestamp: October 04, 2016, 02:21:06 am
content: Only TI could build a TI voltage reference using 10000 TI's voltage references.JS

author: zlymex
author_rank: Frequent Contributor
timestamp: October 04, 2016, 04:32:59 am
content: I once build an 100V reference(with 10V output as well) by stacking 10 LT1021BCN8-10 plus a constant current source. This IC is much better in term of drift and noise.I also had a plan to stack 14 LTZ1000 to obtain a super 100V. For this purpose, I have selected 14 LT1000 that added up to exact 100.000V. The 14 power supplies have to be isolated.

author: daqq
author_rank: Super Contributor
timestamp: October 04, 2016, 07:14:33 am
content: QuoteI'd love to see this approach applied to the 100kV version

author: zlymex
author_rank: Frequent Contributor
timestamp: October 04, 2016, 12:05:17 pm
content: Quote from: daqq on October 04, 2016, 07:14:33 amI'm trying to squeeze one unit as small as possible, for a starter

author: retrolefty
author_rank: Super Contributor
timestamp: October 04, 2016, 12:33:20 pm
content: Quote from: JS on October 04, 2016, 02:21:06 amPretty unusal app. note:Quote

author: JS
author_rank: Frequent Contributor
timestamp: October 04, 2016, 08:56:02 pm
content: Quote from: zlymex on October 04, 2016, 04:32:59 amDo they? Why not to supply one from the reference one before, in some ladder fashion? Maybe separate supply for the reference, which could be 3 or 4 not insulated supplies for all the references.JS

author: zlymex
author_rank: Frequent Contributor
timestamp: October 05, 2016, 02:10:58 am
content: Quote from: JS on October 04, 2016, 08:56:02 pmI didn't quite catch you.LTZ1000 is not operated in shunt mode(2-terminal mode? or zener diode mode) like REF5010 or LT1021, where the supply and the output are the same.The 7.1V output of a LTZ1000 circuit comes from two sense pins which are not the same as the supply rails. Ideally there should be no current flow through these sense pins in either direction(in or out). All the 28 sense pins should be connected in series fashion in order to get a perfect 100V. If any of the 14 power supply is not floated, there would be a current flow through some of the sense pins and degrade the performance to say at least. That is also the reason why devices like REF5010 can be cascaded in the simplest way.

author: JS
author_rank: Frequent Contributor
timestamp: October 11, 2016, 03:35:46 am
content: Quote from: zlymex on October 05, 2016, 02:10:58 amI was thinking on the full configuration for each one, with the output buffer which can source current. Use the output of the opamp to power the next stage, not much juice needed as the previous stage should balance the current. The problem, as usual, would be the heaters. In this config, the ground of the first stage, the pin 1 of LT1013 (or after the diode) of the second and the V+15 of the third should be tied together. Some tweak of the circuit should probably be used to manage the zener - sense terminal. I'm not saying is an easy solution but seems there may be a way, and once solved for one stage would take the need of 14 clean floating voltage supplies.Isn't a better approach (cheaper and more reasonable) to use an amp stage to take that 7V and turn them into 100V? There are really stable resistor networks and you could ovenize them to get even better stability. A pain LT5400 can't handle 100V but can handle 60V without trouble, so two of them and keeping the LTZ in the middle would do it. To complete the circuit two low drift opamps and a few high voltage transistors would be needed.I'd guess the REF5010 approach as a transfer and a KVD to calibrate it to an LTZ makes an easier world to live in.JS

author: Kleinstein
author_rank: Super Contributor
timestamp: October 11, 2016, 02:04:29 pm
content: Stacking 10 references for a 100 V reference makes some sense, if you have a setup (e.g. switches) to measure / calibrate the individual parts too. So you get a 100 V reference and a way to a 10 V to 100 V transfer by adding the individual voltages. As with a 10 V to 100 V transfer this is more about short time stability, the Ref5010 might not be such a bad choice.The problem with a resistive divider is that you have to rely on linearity of the resistors - at 100 V you can't just take it for granted at the sub ppm level. So the resistor way (e.g. hamond divider) is that easy either.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: October 11, 2016, 02:13:28 pm
content: Quote from: Kleinstein on October 11, 2016, 02:04:29 pmAlso with a resistive divider the voltage noise of the reference is multiplied directly (plus the divider would add some noise), but for a stacked 10V references the resulting noise is increased by a square root, so for 10 references the total noise would be only about 3.16 times of the noise from one reference and the relative noise is actually reduced.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: October 11, 2016, 02:56:35 pm
content: Quote from: DiligentMinds.com on October 11, 2016, 02:47:39 pmIt is the same thing.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: October 11, 2016, 03:13:08 pm
content: Quote from: DiligentMinds.com on October 11, 2016, 03:06:57 pmIt is exactly the same for a parallel configuration.CheersAlex

author: Alex Nikitin
author_rank: Super Contributor
timestamp: October 11, 2016, 03:20:43 pm
content: Quote from: DiligentMinds.com on October 11, 2016, 03:16:46 pmTherelativenoise is reduced in the same way for both cases. For the series connection the noise voltage increases by \$\sqrt(10)\$ but at the same time the DC "signal" voltage increases 10 times.CheersAlexP.S. - say, a single 10V reference has 10uV p-p noise. WIth a resistive divider in a feedback loop of an amplifier we'll get 100V and 100uV p-p noise. With 10 references in series we'll get 100V and only about 31.6uV p-p noise.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: October 11, 2016, 03:36:40 pm
content: Quote from: DiligentMinds.com on October 11, 2016, 03:27:45 pmStrictly speaking, if the series connected references are thermally coupled and protected from air movements, than the resulting drift (relative again!) would be not worse that for a single reference and should actually be somewhat better as the references would have a distribution of drifts.Quote from: DiligentMinds.com on October 11, 2016, 03:27:45 pmIt would be as stable as the resistive divider.CheersAlex

author: Kleinstein
author_rank: Super Contributor
timestamp: October 11, 2016, 04:32:35 pm
content: For the series configuration it is not that practical to use chips that are made for a relatively exact 10 V value each, as those tend to have more drift and cost than those that directly output the raw zener voltage. So the more sensible version might have been 14 pieces of LM329 (ideally in a metal case if you can still get them) or those Chinese low noise zeners (2DW..) and than one adjustment to get the exact value of 100 V if needed.In a way the 10 references REF5010 also provides a reasonable accurate 100 V without adjustment. Though at that price I would not mind an adjustment with a good DMM.

author: EmmanuelFaure
author_rank: Regular Contributor
timestamp: October 11, 2016, 11:17:53 pm
content: Quote from: DiligentMinds.com on October 11, 2016, 04:42:24 pmhttp://www.hkinventory.com/?