Author Topic: Regulator question  (Read 1012 times)

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Online neo

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Regulator question
« on: September 30, 2016, 04:43:41 pm »
This may be a question, aka why its here, but why does my regulator have 5 pins?
http://datasheet.octopart.com/LM2941-National-Semiconductor-datasheet-118224.pdf

i plan to use it regulate between 10 and 20v right at an amp
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Online Kleinstein

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Re: Regulator question
« Reply #1 on: September 30, 2016, 04:56:49 pm »
Some regulators use more pins for extra functions compared to the minimal 3 pin configuration for a regulator. The lm2951 happens to have 5 pins used - same cases have even additional unused ones.

Usually it is not a good idea to use such regulator close to there maximum current. The drop out is not that small anymore and heat dissipation gets a problem. The SOA may not even allow for a large drop at full current. So one should look for a larger one, maybe rated for 1.5 or even 3 A. However with additional features like shutdown the choice is not that large.

If it is 20 V in and 10 V out, there is no need for a low drop regulator. Its than usually better to use a conventional one like 7810 / LM317.
 

Online neo

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Re: Regulator question
« Reply #2 on: September 30, 2016, 04:59:14 pm »
what i have is a set of iv-6 vacuum fluorescent displays a ~27v supply and a want to use an adjustable regulator to adjust the voltage between 10 and 20v, the reason i have this specific one is i have them in my parts bin
re-reading the iv-6 datasheet and it wont be quite that high half that at most
« Last Edit: September 30, 2016, 05:02:23 pm by neo »
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Online neo

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Re: Regulator question
« Reply #3 on: September 30, 2016, 05:05:10 pm »
i suppose my question was more or less, what do i do with/about the on off pin
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Online Ian.M

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Re: Regulator question
« Reply #4 on: September 30, 2016, 06:20:50 pm »
Bring it out to a 2 pin header with ground  and put a jumper on it for now to hold the regulator on.  Remove jumper, connect logic output and you can then switch the power to the VFDs on demand.   If you decide to put a pullup there to 27V like the datasheet shows, put it on a 3rd header pin! If you use a mechanical switch, you can connect it to both the pullup and ON/OFF, but it avoids the logic getting 27V stuffed up its chuff which it wont like much.
 
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