Does a TL431 need programming before replacing one in a SMPS ?

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
When you replace a TL431 Regulator that's already in a SMPS, is it necessary to program it before installation or is the circuit already designed to do that automatically whenever a new one is installed?

Thanks
 

dendad

Joined Feb 20, 2016
3,940
If it is the same type number, it should be a drop in replacement.
Altering the voltage is done with the external resistors.
Why do you think it is faulty?
 

Papabravo

Joined Feb 24, 2006
17,316
There is no programming involved in a TL431. It is just a shunt regulator and a comparator. Where did you get the quaint notion that programming was required? Certainly not from the datasheet which you apparently failed to procure.
 

Papabravo

Joined Feb 24, 2006
17,316
To come to @Lumenosity 's defense, it could be confusing to new electronics users...

View attachment 242528
IMHO if you are going to jump to conclusions by reading the title of a datasheet and not digging further, you should probably give up expecting success in designing and building circuits. Programmable features in analog electronics existed in the literature and in practice for decades before there was such a thing as a processor that could execute a stored program. My sympathies are more than non-existent, but less than abundant.
 
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dendad

Joined Feb 20, 2016
3,940
Admittedly, this is an old part, with old terminology, and "adjustable" may be a better term, but as I noted, it can be confusing to new users.
I do not see a reason to post negative comments that could discourage folk to get into the wonderful field of electronics when a well worded explanation could fix the misunderstanding.
People come here for help and I do my best here to encourage folk, not put them down.
 

Papabravo

Joined Feb 24, 2006
17,316
Admittedly, this is an old part, with old terminology, and "adjustable" may be a better term, but as I noted, it can be confusing to new users.
I do not see a reason to post negative comments that could discourage folk to get into the wonderful field of electronics when a well worded explanation could fix the misunderstanding.
People come here for help and I do my best here to encourage folk, not put them down.
I gave a succinct description of the part and asked where the notion came from. Identifying the source of misinformation or misinterpretation seems like it might be a relevant thing for the TS and other readers of this thread. I hardly think I was offensive. Why did you think it was?
 

dendad

Joined Feb 20, 2016
3,940
I did not say your comment was offensive, but, if you would accept some critique, "quaint notion" is condescending.
And, IMHO, "Certainly not from the datasheet which you apparently failed to procure." is making an assumption, particularly as it has "Programmable" in the data sheet title.
@Lumenosity was not trying to design or build a circuit, but to fix an existing one.
 

Dodgydave

Joined Jun 22, 2012
10,095
When you replace a TL431 Regulator that's already in a SMPS, is it necessary to program it before installation or is the circuit already designed to do that automatically whenever a new one is installed?

Thanks
NO, it should give the same output there is no programming involved, just the resistors to set the voltage.
 

Papabravo

Joined Feb 24, 2006
17,316
I did not say your comment was offensive, but, if you would accept some critique, "quaint notion" is condescending.
And, IMHO, "Certainly not from the datasheet which you apparently failed to procure." is making an assumption, particularly as it has "Programmable" in the data sheet title.
@Lumenosity was not trying to design or build a circuit, but to fix an existing one.
Well I don't accept it because maybe your dictionary has a different set of meanings for quaint than mine. It is also factually correct that the datasheet for the TL431 contains no substantiation for the meaning of "programming" associated with the TS's original question. I think you're trying to pick a fight for no real reason except to pick a fight. I'm not interested.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
If it is the same type number, it should be a drop in replacement.
Altering the voltage is done with the external resistors.
Why do you think it is faulty?
Thank you for your kind response and assistance.
I did in fact read the entire datasheet and even downloaded it for future reference.
In addition, I watched as many YouTube videos on this topic before posting and still was not able to clarify if programming externally was needed before replacing.

It is very helpful that you told me it does not need programming before replacement. Thank you.
As you pointed out, the manufacturer's Data Sheet clearly has "Programmable" in the tile

Perhaps PapaBravo is just having a bad day. There is no reason or excuse for his condescending tone.

TL431DatasheetFirstpage.jpg
 
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BobTPH

Joined Jun 5, 2013
4,054
The thing that is quaint is the use if the word “programmable” in the datasheet.

There was an old book / movie entitled “When We Were Young and Gay.” I would not fault a gen-Z who misinterpreted its meaning.

Bob
 

djsfantasi

Joined Apr 11, 2010
7,935
If you don't want a fight then you might try being a little less condescending and abrasive.
OMG! What’s happening? People complaining about condescending attitudes. Notice they not addressing a posters problem. Which is the purpose of this forum.

Let’s return to the non-judgements and helpful roots of AAC.
 

Irving

Joined Jan 30, 2016
2,322
It would be quite unusual for a TL431 voltage reference to fail, so I'll ask @Lumenosity what evidence have you for that, and how did you test it? I would expect its failure, if it has, to be as a result of something else failing in a very significant way...
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
It would be quite unusual for a TL431 voltage reference to fail, so I'll ask @Lumenosity what evidence have you for that, and how did you test it? I would expect its failure, if it has, to be as a result of something else failing in a very significant way...
In all honesty, the thread is not really about how or why it failed or how I came to the conclusion, it's only about whether or not it needed programming before replacing. Getting into that discussion might derail the primary question of the thread.

That said,
I believe in this instance the device was connected reverse polarity and yes, I tested it after absorbing multiple YouTube videos on that subject.
I'll go one further in the spirit of cooperation.....it's "possible" I damaged it during removal to test it...honestly not really certain at this point.
 

MrChips

Joined Oct 2, 2009
24,651
The straight answer is: No, the TL431 does not need programming.

The heading of the datasheet states TL431 / TL432 Precision Programmable Reference.

You are thinking of programmable within the context of computer programming.
The word programmable is used in a different context, meaning presettable or adjustable.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
636
The "programming" is done by two external resistors, which would already be in the circuit if you are replacing the device on a PCB.
:) Thanks. I suspected that originally. (See Opening Post)

When you replace a TL431 Regulator that's already in a SMPS, is it necessary to program it before installation or is the circuit already designed to do that automatically whenever a new one is installed?

Thanks
 
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