TL431A: TL431

Andriy Orlyk

Part Number: TL431A

Could someone please confirm if I correctly implemented TL431A regulators instead of zener diodes?

I need TL431 to be used for 5V and 15V supply. For 5V I used two 5K resistors from Ref to Cathode and Anode; for 15V I used 23.5K to Cathode and 5K to Anode from Ref.

Thanks.

over 7 years ago

0 Vincenzo Pizzolante over 7 years ago

TI__Mastermind 22756 points

hi Andriy,

you just need to apply equation in fig.21 on page 18 of the device datasheet, keeping Iref << Ika and Ika >= 1mA all the time.
so for the 5V it is correct, R1 = R2; while for the 15V has to be R1 = 5 x R2.

hope this helped a bit
KR
Vincenzo

0 Andriy Orlyk over 7 years ago in reply to Vincenzo Pizzolante

Prodigy 50 points

Hi Vincenzo,

Thank you for your reply. So, I should change 23.5K to 25K to get 15V on TL431 in this schematic: drive.google.com/.../view

I got 150 by this equation in fig.21 on page 18. By equation on ART. 10.2.2.2.1 on page 24 i GOT 372.5

BR,

Andriy.

0 Vincenzo Pizzolante over 7 years ago in reply to Andriy Orlyk

TI__Mastermind 22756 points

yes.

for the 5V you can see how the schematic shows 5K / 5K (R1=R2) , while for the 15V it is 25K / 5K (R1=5xR2) (in the schematic probably is a nominal 15V; indeed using 23.5K instead of 25K will give 14.2V)...

KR
Vincenzo

0 Andriy Orlyk over 7 years ago in reply to Vincenzo Pizzolante

Prodigy 50 points

Thank you Vincenzo!
Very appreciate your help, indeed I need 15V and have to use 25K.
My Best Regards,
Andriy.

0 Vincenzo Pizzolante over 7 years ago in reply to Andriy Orlyk

TI__Mastermind 22756 points

hi Andriy,

a very last thing...
I saw in the portion of the schematic you sent big resistor (with high power rating) limiting the current into the TL431 block...
I don't know the function of the circuit becasue I don't have it entirely, but consider that the new ATL431 requires a minimum IAK of 40uA instead of 1mA of the TL431... the price to pay is that the frequency response of the ATL431 is much slower than TL431...
just in case you weren't aware...

KR
Vincenzo

0 Andriy Orlyk over 7 years ago in reply to Vincenzo Pizzolante

Prodigy 50 points

Hi Vincenzo.

Here is the full schematic. This is audio amplifier.
drive.google.com/.../view
What do you think, perhaps I don't need in this case 2.2K or\and 100MT, only 2.2K 2W is enough in the schematic?

BR,
Andriy.

0 Vincenzo Pizzolante over 7 years ago in reply to Andriy Orlyk

TI__Mastermind 22756 points

hi Andriy,

I see... well, it should work even if you need to tune it up, plus the resistors have to be 1% or better to avoid mismatches...
I would also consider a monolitic solution, like the TPA3255 ( www.ti.com/.../tpa3255evm ) or, even better, the reference design PMP11769...

KR
Vincenzo

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TL431A: TL431