Whatever happened to Rejustors?

[splin]

These electrically adjustable resitors from Microbridge Technologies seemed quite a neat alternative to trim pots - datasheet: http://datasheet.octopart.com/111N-Microbridge-Technologies-datasheet-8331023.pdf

But apart from some publictity in 2007 and a few later references they don't seem to be available. Even the Microbridge Technologies website demands a password. The company still exists as far as I can tell, so does anyone know what happened? Did they fail to manufacture these products to specification? Might they still be in gestation?

[Lightages]

Interesting device! I had never heard of this one before.

[Kleinstein]

I have not heard of these chip before. The llimmitiations I saw from the Datasheet is the very limited power handling capability: due to the effect of self heating even 1 mW can be too much for precission applications. Also the range for adjustment is rather limited. This may be good in some cases, but digital pots are often more versertile.  Also thermal stbility is not that good - possibly too bad for precission circuits.

[T3sl4co1l]

Controlling an LM317?

That 1mW power limit puts a bit of a drag on how much of that you can do..

Tim

[c4757p]

I have not heard of these chip before. The llimmitiations I saw from the Datasheet is the very limited power handling capability: due to the effect of self heating even 1 mW can be too much for precission applications. Also the range for adjustment is rather limited. This may be good in some cases, but digital pots are often more versertile.  Also thermal stbility is not that good - possibly too bad for precission circuits.

I wonder whether it's something that could have been improved if they ever had the popularity to support the R&D.

[splin]

They obviously have some important limitations, but unlike digital pots they don't (didn't? wouldn't have if they could actually have made them to spec?) require power after they have been adjusted. I'm sure there are plently of application areas where they would be useful - one example described is for calibrating Rowowski coils (current sensors) which are passive devices and operate at very low signal levels where the 1mW limit is irrelevant.

This outlines how they work and describes an instrument amplifier using them:

http://electronicdesign.com/analog/sensor-conditioning-amps-use-rejustors-precision-compensation

This is only of academic interest though if they aren't ever likely to see the light of day. I wonder if the long term stability was a significant problem given:

For trimming, the power resistor is pulsed in a controlled fashion, briefly raising the temperature of the adjacent Rejustor resistor. The result is an annealing that changes the requestor’s resistance in a controlled and predictable manner. The annealing takes place at temperatures far above normal operating temperatures.

The price was quoted as $.99 @ 1k in 2007 press releases which doesn't seem too bad. Perhaps the limitations meant the market looked to be too limited so they abandoned development?

[Lightages]

They don't need power after being set. These would be great for some uses if they are stable. If so, they would be much better than trim pots in many things.

[splin]

... and this application was quite interesting as it involves adjusting the Rejustor's temperature coefficient (which I hadn't appreciated was one of its important features) as well as its resistance value to compensate an ADR 425A voltage reference to improve its TC from 10ppm to .8ppm, at acost of circa $0.5:

http://www.powerguru.org/get/

Shame you can't seem to get them.

[Lightages]

They were a Canadian company too! Their website doesn't exist. I am very surprised these didn't make it into many test instruments. There must have been some "gothca".

[eas]

A little googling turned up that the company was acquired in 2011 for a different product (a flow sensor) they developed.

[amyk]

It seems somewhat like a memristor.

I guess non-volatile digipots are easier to interface with and have displaced them.

[technix]

Big problem for their product: needs special, proprietary software to adjust, and range isn't that good. Nonvolatile digipots, even volatile digipots coupled to cheap MCUs with embedded EEPROM (or even a small external 24C02,) largely displaced them all.

If my project board have a few calibration points I will more likely be using d-pots, since calibrating is a lot easier (e.g. add a small voltage reference chip like MC1403 and calibration points can be adjusted internally using the MCU's built in ADC as feedback)