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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.

67 questions
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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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TL431 on-mode voltage

The TL431 datasheet mentions that the VIKA is approximately 2 volts (when the input is more than Vref = 2.5 V), but based on my simulation, it shows me (1.07 V to 1.2 V). I need to know where I can find the VKA on-voltage based on the datasheet.
John Jin
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Difference between TL431 and TL432

What is the difference between these parts? The datasheet shows completely different pinnings, but both are specified over the same range and both have the A, B and ungraded specifications for tolerance. Just curious.
Thomas O
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Undervoltage detection using TL431 with high rail voltage

I want to use the circuit below to detect undervoltage at the input. I don't have any other supply but the input voltage, so I should use the input voltage as supply voltage. The problem is that the input varies from 36 to 110 V and the TL431 can…
Erfan Mirhoseini
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TL431 as negative voltage reference

Im building a LM317 based power supply and the output range must be 0.3V-21V. I've used a 2 diodes in series and a resistor supplied by a negative voltage and take the node between resistor and diode to be a negative reference to be fed to the…
rlmarco
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Configuring a TL431 current limitation

I am trying to get this well known circuit [ work inserted in a series of 69 LEDs to protect them according to this specification. Transistor is 2N2222, hfe=18 according to multimeter. The free-running current is 19mA and I use Rcl=100R to limit…
Papou
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TL431 constant-current source voltage drop

Is it possible to somehow eliminate or reduce the TL431 constant-current source voltage drop? I have studied this application note from TI. In my opinion, it nicely presents the possibilities of using the TL431, especially in relation to the current…
OH1LLN
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How can I calculate the max. allowable load for my reference voltage?

I have a 2.5V reference voltage set up like so: I want to determine how many ohms in load this 2.5V can bear before the TL431 is unable to hold the voltage. I know that this IC requires 500uA to 1mA in order to regulate the voltage. How would I go…
Ozbekov
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TL431 output wrong

The purpose of the circuit below is to get a V_cathode of 2.5V (Vref) when VDC is higher than 10.4V approximately. The problem is that when VDC>10.4V the voltage checked in V_cathode is 1.9V instead of 2.5V. 3V3_UC_PIN comes from a microcontroller…
robocotec
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TL431 Resistor Choice

I read the Christophe Basoo article The TL431 in Switch-Mode Power Supplies loops: part II About how to choose the resistor I have some questions I would like to ask. On page 13 and page 14 (Watch the LED series resistor value) There are my…
Jitter456
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What's TL431 Output voltage

I am using PSIM to simulate the TL431, and I have some questions. This is my PSIM circuit: When Vref is less than 2.5V, the TL431 doesn't conduct, it looks like an open circuit so Vo is almost 5.1V. When Vref is higher than 2.5V, the TL431…
Jitter456
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LED resistor in the TL431

I read the Christophe Basso APEC 2011 seminar, about this figure I have one question. 1.) Why RLED,max need to below this equation(Red line), what happen if RLED above this equation(Red line)
Jitter456
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TL431 Extracting the Pole

I read the Christophe Basso APEC 2011 seminar, about this figure I have some things I can't get it. 1.)Why should need to put the Cdc capacitor in the circuit, what's this function? to block the DC source? 2.)Why need to let Vfb at 2-3V, how to make…
Jitter456
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TL431 Type2 Compensator derivation

I am trying to derive the Type 2 Compensator by using TL431, and I read the C.Basso document and I know how to derive the Type 1 Compensator, but I don't know why adding the capacitor (C2) at the Vfb will generate a pole and get this equation (the…
Jitter456
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TL431 small signal analysis

I read the Chris Basso APEC 2010 I don't understand why the C1 can connect the Op amp output directly when using the TL431. Because the TL431 output has a BJT.
Jitter456
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