Hello all,
Hello Warren,

after having experimented a lot with 5V monolithic zener references
and still not found the ideal solution I want to try a 1N82x based solution.

For me a extended room temperature range of
25 degrees centigrade +/- 7 degrees (64-90 °F)  is of interest.
Since I plan to have battery supplied instruments a lower supply current would be of interest.

For the zeners a zero TC current is stated.
Over which temperature range the TC is nearly zero.
How large is the voltage deviation in the above mentioned range?

Does it play a role for the absolute temperature deviation if a 1N823 or a 1N829 is used?
Or is the behaviour equally when the individual zero TC current is used?
Is the only difference between the selections that the zero TC current is more near the 7.5mA value on the 1N829?

So is it more likely to get a low zero TC current of 4 mA on a 1N823 device than on the 1N829?
Or should I go for the 1N829A for the lowest absolute TC?

How large is the hysteresis on the zeners in a temperature range of 10-40 degrees celsius (50-104°F).
On monolithic unheated reference voltages with hermetic case I have up to around 2 ppm hysteresis difference
on temperature cycling. (see attached picture with 10-45 degrees celsius on X-Axis for an ADC with a 5V reference
measuring a LM399 heated reference over a 2:1 precision voltage divider. The ADC with the 5V reference is temperature cycled).

I blame the temperature hysteresis on the die attach to the lead frame which seems to be usually a silver filled epoxy compound.
I hope that the hysteresis on a discrete zener is much lower.

With best regards

Andreas

Don't bother with TC zeners, especially for battery operated equipment.
There are lots of nice IC references available from Analog Devices,
Maxim, Linear Technology, TI, an so on, that will run rings around TCZs

• you probably haven't seen the right one yet. The TCZs will only
  provide near zero tempco at one temperature only, so would have to be
  ovenized to get best performance. They also have an initial voltage
  tolerance up to a few percent, so the circuit would need tweaks and
  maybe amplification that add more error yet. I doubt that any TCZ will
  match an LM399 even with very elaborate circuitry to support it.

I think the Maxim MAX3650 family would be hard to beat for a low power 5
V reference - my super-duper voltage standard (yet to built) will use
four of them averaged together, and operated at constant temperature.

If you state what kind of performance you're looking for, it would be
easier to make recommendations.

Ed

Hi, Andreas!

AJ> I want to have high end specs with the power consumption of a battery
AJ> supplied DMM.
AJ> that is:
AJ> tempco below 1ppm/K
AJ> hysteresis in the 10-40 degree range well below 1ppm
AJ> no sensitivity to humidity (so all plastic housings will fall out)
AJ> ageing in the range of 1 ppm/year after some pre-ageing

I did a lot of references with LTZ1000, LM399 and aged zeners, but
it is not easy to achieve these specs even with LTZ1000. One of the best voltage
standard Datron 4910AV (4x LTZ1000) have only 1 ppm/year drift.

Regards,
Mickle T.