[volt-nuts] LTZ1000A Heater Temp

[Frank Stellmach]

Hello Ben,

sure, this has been discussed intensively, also on:
http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/

85°C is NOT commonly used neither for LTZ1000A, nor for LTZ1000.

Only in the HP3458A, the LTZ1000A is mistreated, running on about 95°C.

Usually, if the LTZ is run w/o further heat sources in the surrounding 
applications, you may run the

LTZ1000 : 45°C, 12k / 1k (gives about -0.8ppm/year stability)
LTZ1000A: 55°C, 12k5 / 1k
LTZ1000x: 65°C, 13k / 1k (see datasheet)

50°C will be somewhere in between.

LTZ1000 and LTZ1000A both use the very same die (chip), but a different 
die attach epoxy.

The A version therefore is thermally more isolated from the TO99 case 
(400°C/K) than the non-A version (80°C/K).

Therefore, the A version heats up 10°C higher than the non-A, due to the 
self heating effect caused by the reference circuit itself, and 
therefore must run 10°C higher; 45°C or even 40°C is not feasible for 
the A version.

I always recommend the LTZ1000, non-A version, on 45°C for best 
stability, and it's also much cheaper.

Frank