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Questions tagged [tl431]

For questions about the three-terminal shunt regulator. Use in conjunction with the "voltage-regulator" or "voltage-reference" tags, as applicable.

For questions about the three-terminal shunt regulator. Use in conjunction with the or tags, as applicable.

See the TL431 datasheet for more information.

62 questions
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Does the TL431 have a "dropout voltage" per se?

I want to get a stable 3V reference from a +3.3V ±5% supply (so it can go as low as 3.135V and as high as 3.465V.) I know the TL431 is a shunt/zener regulator, so doesn't really have a dropout voltage, but there probably is some point above 3V at…
Thomas O
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TL431 fast lane and slow lane

I read AN_201610_PL16_01 (Using the IRS2982S in a PFC Flyback with opto-isolated feedback) from Infineon. I would like to know what the fast lane and slow lane are. The document doesn't explain it in detail. Can someone explain it?
Jitter456
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8
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3 answers

Crowbar circuit causes unexpected behavior for op amp circuit

I am using an op amp to amplify an input signal from a microcontroller, which in general is working fine. For over voltage protection, I added the crowbar circuit taken directly from figure 32, page 27 of the TL431 data sheet and that added some…
Eye of Horus
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7
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6 answers

Power cutoff for car when power drops below 13V

I just bought a 2004 Explorer. I have a wireless phone charger and GPS plugged into the cigarette lighter port. The problem is this is always on even when the car is off so I'm forced to unplug everything when I shut the car off. Not a huge deal,…
hdelien
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6
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1 answer

TL431 as a comparator?

One of the things I've noticed in a few power supplies is the use of a TL431, a voltage reference, as a comparator of sorts. It seems to be set up in a configuration where when the voltage across it exceeds some point, it conducts, and this turns on…
Thomas O
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6
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2 answers

TL431 low battery cut-off

Could somebody please explain the operation of the attached diagram? The circuit was proposed here and here as a low voltage cut-off circuit, which switches off the MOSFET when the voltage drops below the reference voltage set by the voltage…
Egon
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6
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5 answers

TL431 Constant current source

I have few doubts regarding TL431. Please correct if i am wrong.. TL431 can be used to generate voltages from Vref to 36V. Output voltage is taken across diode in reverse biassed condition. reverse characterstics says Reverse breakdown voltage is…
user19579
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5
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2 answers

Is this TL431-based overvoltage limiter circuit alright?

I have a supply rail that is 15 V nominally +/- 5%. So the highest nominal voltage is 15.75 V. Due to external fault currents of up to 200 mA, the voltage on this rail can rise anomalously. The fault currents are cut out by additional circuitry…
tobalt
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5
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1 answer

TL431 crowbar simulation problem

I'm trying to simulate crowbar circuits, which is mentioned on page 8 of ON SEMI TL431 datasheet (https://www.onsemi.com/pub/Collateral/TL431-D.PDF). I'm using TINA TI for this. There are two circuits, one with TRIAC, another with SCR. Trip voltage…
Zhenek
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4
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1 answer

compensation for flyback regulator with 431 and optocoupler

I am testing a flyback converter with secondary side regulation, by means of a 431 in conjunction with an optocoupler with nominal CTR of 50-100%. A snippet of the regulator part is below. I have used the 431 before to regulate non-isolated supplies…
tobalt
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2 answers

TL431, take two

I'm using a TL431B (±0.5%) shunt regulator to get 3V ±1% (max.) from a 3.3V ±5% supply, so from 3.135V to 3.465V. The 3.3V supply is a switcher, so has a decent amount of high frequency (~3 MHz) noise on it. This is related to my previous…
Thomas O
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4
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1 answer

I'm trying to build a lipo discharger

The way I want it to work is to slowly discharge the lipo down to storage voltage and then stop. I think the best way to do this is to use a TL431 to control the voltage shutoff and use a power resistor and status LED as a load. I don't really…
japhillips87
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1 answer

Strange oscillations with TL431 voltage reference

I have a problem with TL431 voltage reference circuit: There is no load connected to VREF25. When I remove C8, voltage VREF25 is perfectly stable 2.5V. But when I put C8 back into the circuit, voltage VREF25 is oscillating and I can't figure out…
Chupacabras
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3
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2 answers

Is this component in falstad a tl431

I'm self studying electronics, I am now familiarizing myself with the tl431, which is pretty much a "variable zener" aparently. I was shown the following symbol. I would like to simulate some circuits with it on falsad, I found this component, that…
Joaquin Brandan
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3
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Ripple in output voltage

I am working on an Active Clamp Forward converter. Schematic is given here: Specs: Output voltage-5V Input voltage 26..42V frequency=500KHz Output power=10W It is working fine in open loop, but in closed loop I am getting a ripple in output…
Archit Asthana
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