TL431 BIAS RESISTOR CALCULATION

168

Other Parts Discussed in Thread: TL431, TL432

HELLO, DEAR TI ENGINEER:

i am designing a REF circuit for my project, and i want to use the ic TL431, but i meet with two questions:

1: what is the differences between TL431 AND TL432?

2:how to calculate the bias resistor R? see the attached pic. my input is +5V, AND the output is +3v. i mean: the VI(BATT) IS +5V, THE VO IS +3V.

THANKS VERY MUCH. URGENT!!!

over 12 years ago

0 Ron Michallick over 12 years ago

TI__Guru**** 164796 points

168,

The difference between TL431 and TL432 is the pin out. Setting the shunt voltage on an adjustable shunt regulator application note

0 Ron Michallick over 12 years ago in reply to Ron Michallick

TI__Guru**** 164796 points

168,

The input resistor between 5V (in) and 3V (out) needs to provided at least the maximum application load current plus 1mA. R<=(5V-3V)/(Imax+1mA).
At minimum output load current the TL431/2 cathode current must be less than 100mA. Ik<=(5V-3V)/R - Imin. Power in resistor is (5V-3V)^2/R.

0 168 over 12 years ago in reply to Ron Michallick

Prodigy 90 points

thanks for ur detailed explnation. i can continue my design now. thanks again...

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TL431 BIAS RESISTOR CALCULATION