[volt-nuts] Trimming the LTZ1000 tempco

[Andreas Jahn]

> However the tempco matching isnt perfect with a "typical" (note sample 
> size = 1!!!!) residual of +50ppm/K (+350uV/K)

I would not talk of a sample size = 1.
My LTZ #1 has  48ppm/K with 70k and 52ppm/K with 50K
My LTZ #2 has  54ppm/K with 70k
Both have a setpoint divider of 12K5/1K.

and:

from the datasheet you can calculate for the 13K/1K nominal temperature 
setpoint
100 ppm in voltage divider change R4/R5 will give 1 ppm output change.
100 ppm change of 0,5V VBe will give around 50uV temperature setpoint 
change.
2mV VBE/K or 50uV/2000uV/K = 0,025K temperature setpoint change.

So from datasheet with nominal divider you can calculate
40 ppm / K typical temperature gradient.

>From Mickles "LTZ-guru" we can calculate 39ppm/K for the
unheated reference. (0.95ppm output for 100ppm divider change)

So there seems to be less tempco (but faster ageing)
 with higher temperature setpoints.

With best regards

Andreas