[volt-nuts] LTZ1000 at higher currents

John Devereux john at devereux.me.uk
Fri Oct 21 11:47:41 UTC 2011


Yes I am assuming a LTZ1000 (not A) and 20C lab environment.

Could you clarify your remarks about cooling, I can't tell if you mean
poor cooling (good insulation) or good cooling (heatsink somehow)?  

I was wondering about oil immersion too.



m k <m1k3k1 at hotmail.com> writes:

> Hi John,
> The LTZ1000 can be run much harder, but the LTZ1000a can only be run upto about 40-45 mA before the chip temp is up to 125C where the dift is going to be much higher.
> I am assuming a 20C lab environment for homebrew kit with decent cooling. But to stop thermal drift you really have to give the chip and pcb poor cooling or dip in parrafin oil.
> Regards,
> M K
>> From: john at devereux.me.uk
>> To: volt-nuts at febo.com
>> Date: Wed, 19 Oct 2011 14:14:45 +0100
>> Subject: [volt-nuts] LTZ1000 at higher currents
>> Hello everyone,
>> Is there some reason why LTZ1000s are not run at a lot higher current
>> than 5mA?
>> Thermal resistance is 80'C/W, or ~0.5'C/mA. So it would seem OK to run
>> it at 10, 20, 30mA before seeing serious problems due to raising the
>> temperature too high. 
>> The datasheet noise graph shows a big fall in noise level between 1 and
>> 5mA, so this ought to reduce the noise further. I am not sure how far
>> down in frequency this improvement continues. On the datasheet the
>> "noise gap" widens more and more with lower frequency, does this extend
>> to frequencies so low they would be regarded as long term drift? 
>> There is no current limit for the zener that I can see (of course there
>> will be one eventually). 
>> The "Pickering patent" uses pulsing to achieve a high current in what is
>> obviously a LTZ1000, the stated reason being to minimise "VLF and long
>> term instability".
>> But it seems like even a higher DC current could be of benefit.


John Devereux

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