LT1034 burried zener

[zhtoor]

hello friends,

i was wondering if anybody had had any experience with using LT1034 burried zener (7V) and
its stability / noise characteristics?

regards.

[RandallMcRee]

But its a bandgap reference, right?

[BNElecEng]

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?

[Gyro]

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- The hermetic package is obsolete.

[RandallMcRee]

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?

[BNElecEng]

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.

[zhtoor]

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 ltz1000
like assembly?

as always, comments shall be highly appreciated.

[Gyro]

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.

[ManateeMafia]

How about something like the MAT01? Hermetic and they are matched.

[zhtoor]

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.

true, 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.

[zhtoor]

- No on-chip temperature sensor (unless you can use the bandgap ref in some way - unlikely).

hello,

how about using the bandgap in *forward* mode? (have a look at forward characteristics in the datasheet)

regards.

[BNElecEng]

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.

[zhtoor]

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.

correct. 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 ranges
ca. 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.

[zhtoor]

hello friends,

has anybody measured the tempco of the auxilliary burried zener in LT1034,
is it in the region of ca +2mv / degC ?

regards.

[bopcph]

hello friends,

has anybody measured the tempco of the auxilliary burried zener in LT1034,
is it in the region of ca +2mv / degC ?

regards.

40ppm/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 on 

I 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 

[zhtoor]

hello friends,

has anybody measured the tempco of the auxilliary burried zener in LT1034,
is it in the region of ca +2mv / degC ?

regards.

40ppm/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 on 

I 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 

thanks.

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 thermally
coupled 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 samples 

regards.

-zia