TL431LI: Why is it that some references have 2.495V as their nominal reference voltage and some have 2.5V ?

Michael Ernst

Part Number: TL431LI
Other Parts Discussed in Thread: TL431, ATL431

Hello,

my question is maybe Kind of stupid but please forgive me for that, but I'm curious ;-)

Why is it that there are *431* references on the market which have 2.5V as there nominal voltage and some have 2.495V ?

Does it come from differences of the internal schematic, or is there some technical reason why 2.495V is/was a well Chosen value?

Furthermore, depending on the answer to the previous question, is one value more common than the other nowadays?

Would be great if someone could help me out here.

Thanks in advance,

BR Michael

over 5 years ago

0 Trailokya Rai over 5 years ago

TI__Genius 11311 points

Hi Michael

ATL devices are trimmed to 2.5V and TL devices are trimmed to 2.495V. Internal circuit is same.

Regards

Trailokya

0 Michael Ernst over 5 years ago in reply to Trailokya Rai

Prodigy 110 points

Hi Trailokya,

yeah, i got that.

But why trimmed to this "obscure" value 2.495 ?

BR Michael

0 Trailokya Rai over 5 years ago in reply to Michael Ernst

TI__Genius 11311 points

Michael

I will confirm with the team and let you know.

Regards

Trailokya

0 Marcoo Z over 5 years ago in reply to Michael Ernst

TI__Mastermind 19550 points

Hi Michael,

There is no straight forward answer since the device was designed ages ago. One reason I believe this happened is that the output of the TL431 is Vout = 2.945 * (1 + R1/R2) + R1 * Iref. Due to the R1*Iref term, the output voltage was scaled down a bit to compensate with R1.

This i why ATL431 is a 2.5V because its Iref is so much smaller that R1*Iref has less impact. But at the end of the day, its still speculation from my side. We have no clear answer to this question.

-Marcoo

0 Michael Ernst over 5 years ago in reply to Marcoo Z

Prodigy 110 points

Dear Marcoo,

thanks for your answer.

This explanation sounds reasonable to me.

Have a nice day

Michael

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TL431LI: Why is it that some references have 2.495V as their nominal reference voltage and some have 2.5V ?