[volt-nuts] LTZ1000 at higher currents

m k m1k3k1 at hotmail.com
Wed Oct 19 18:41:14 UTC 2011


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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