In order to understand the dynamics of the LTZ1000 temperature
regulation loop better in order to estimate the chip temperature
response due to ambient temperature fluctuations, I am attempting to
produce a model of the thermal impedance of the chip by fitting a Foster
RC ladder (later transforming this to the equivalent Cauer filter) to
the transient thermal impedance charateristics of the LTZ1000.
The datasheet curves for the transient thermal impedance for the LTZ1000
are inconsistent (they indicate a junction to ambient thermal resistance
of around 170C/W) with the tabulated thermal resistance (unless this is
just the junction to case thermal resistance - the datasheet doesnt
actually specify which thermal resistance junction to case or junction
to ambient is specified.)
Has anyone obtained transient cooling curves for the LTZ1000 to compare
with the datasheet curves?
Even a measurement of the junction to ambient temperature difference as
a function of heater dissipation would be useful.
Whilst monitoring the chip temperature when the heater is driven with a
fixed power as used when measuring the transient thermal impedance is
easily done by measuring the Vbe of the temperature sensing transistor
Q2, monitoring the temperature of the LTZ1000 chip is a little tricky
once the temperature regulation loop is closed as the temperature
sensing transistor Q2 can no longer be used to sense chip temperature
fluctuations.
However the base emitter voltage of Q2 could perhaps be used for this.
Bruce
_______________________________________________
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
