[volt-nuts] Low Frequency noise on LTZ1000A and tempco ofunheatedLTZ
Andreas_-_Jahn at t-online.de
Tue Nov 2 21:31:36 UTC 2010
> Well, do not add too many capacitance, otherwise the temp regulation may
> get stuck,
> heating the element to over 100°C, which may cause drift.
> regards Frank
10nF * 10K or 100nF * around 10K will give a time constant of 0.1 .. 1ms.
The thermal time constant that I have observed is in the range of around
100 ms. So the distance should be enough as long as the output does not
On the other side the unbuffered output is very critical. By accidently
loading the output by an unpowered ADC the LTZ-cirquit has drawn about 75mA
(against 20mA in steady state). Shorting/loading the output of the
unbuffered LTZ will set the heater setpoint temperature to a very large
value. I observed that after this treatment the output was shifted by -11uV
(-1.5 ppm). The shifted value lasted as long as I did several power-cycles
with off-time > 2min to cool down the reference.
After 3 or 4 powercycles the old value was restored. So there seems to be
some thermal hysteresis for large temperature excursions. Unfortunately the
hysteresis is reached even by connecting of a 1uF capacitor at the output of
Do you have a buffering cirquit on your devices? Im looking for a cirquit
which does not add to thermal drift and noise. And is not sensitive to
EMC-noise of course.
with best regards
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