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Need help in analysing this LM317 ckt

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cameo_2007

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Hi,

Please have a look at this LM317 reg. I just find a kind of configuration on the ADJ pin of the chip.A voltage reference.
Any clue on what is that helping for, as the chip also has a 1.25V reference.


vpp.jpg
The data sheet for one of the component,TL431 can be found here http://www.datasheetcatalog.org/datasheet2/3/074yxfos2h5s8aukijk5yg8id7fy.pdf
 
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alexan_e

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There is something wrong with your attachment, when I click them I get "Invalid Attachment specified. If you followed a valid link, please notify the administrator"

Alex
 

FvM

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Any clue on what is that helping for, as the chip also has a 1.25V reference.
The circuit possibly intends a better load regulation than achievable with a single LM317. It's however not obvious, that the feedback loop is stable at all.
 

ea.arun

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generally an extra feed back by using a configurable reference like TL431 is added to achieve a lower output voltage by introducing a different feedback than generally done by feeding the output directly through a voltage divider(or to cheat the eror amplifier of the LDO:wink:)......here the purpose should be a better load regulation.....
 

ea.arun

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cameo : i found onw with a similiar configuration.....refer page number 8 with a different linear regulator.....they have explained the function but maynot be relevent for this application but as a reference....
**broken link removed**
 

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