To go beyond the max voltage rating, one can stack two ( or more TL431 ) .
For instance, to acheive 48 volt one could use two devices serie connected to get twice 24 volt with a chain of four resistors 1,25K, 22.75K, 1,25 K, 22.75K.
Do you see any draw back to this.
This will have all the caracteristics of a single TL431 with two resistors 2,5K, 45.5K
This could also be used to spread the power to several devices.
This, I think is compatible with denoisering as Elvee does with a LM317 and shown successfull with a LT431.
For instance, to acheive 48 volt one could use two devices serie connected to get twice 24 volt with a chain of four resistors 1,25K, 22.75K, 1,25 K, 22.75K.
Do you see any draw back to this.
This will have all the caracteristics of a single TL431 with two resistors 2,5K, 45.5K
This could also be used to spread the power to several devices.
This, I think is compatible with denoisering as Elvee does with a LM317 and shown successfull with a LT431.
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It's important that the voltage devides equally between the two derives, especially under transient turn-on/off conditions. Could be tricky.
You can cascode a TL431 with a MOSFET (or BJT). You need a divider for more than the reference voltage anyway. Just connect the gate part-way down the divider. The TL431 can be a small part of the total voltage for a high voltage shunt, a lot more than 2x36V.
They will devide according to the resistors. There is no need for accurate resistors.
The usual use of TL431 is to implement a Zener diode who' s voltage is programmable with two resistors.
There should be no trouble to have two such Zener diodes connected serialy to add their voltage.
The usual use of TL431 is to implement a Zener diode who' s voltage is programmable with two resistors.
There should be no trouble to have two such Zener diodes connected serialy to add their voltage.
There is more than one way to skin à cat.
The MOSFET or BJT Is likely to cost more than a TL431 ( $0.25 ). With my way you do not need to source another part type.
Using two TL431 to go beyond the 36 volt max rating, up to 72 volt, one can do with 3 resistors, instead of four as said before.
For instance, to acheive 48 volt, use a resistor chain : 1K25K, 24K, 22K75. ( The 24K merges the two middle resistors ).
There is no need for precision resistors, it will stabilise at voltages inforced by the resistors and the TL431 that want to see 2.5 volt at their Ref input relative to their anode.
To go up to 108 volt can be done with 3 TL431 and 4 resistors. Up to 144 volt with 4 TL431 and 5 resitors.
And so on; Each 36 volt extension asking for 1 TL431 and 1 resistor more. The sky the limit, with no need to source other parts type, just replicating with parts you already have. Not bad for an IC that costs less than 25 cents.
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There are plenty of MOSFETs that cost more than $0.25 but many are as cheap as $0.025. Considering that the TL431 is limited to ~500mA, there is no point of using a MOSFET larger, except for high power, which is something another TL431 will not provide. The TL431 is intended as a reference and not the shunt regulator for any amount of power. There is also the issue of noise which becomes a problem when you multiply a small reference voltage by a large number, including TL431 and LM317 etc.
TL431 is like a programmable Zener, so use a normal Zener diode in series.
Adjustment range is limited, but that might be acceptable.
Adjustment range is limited, but that might be acceptable.
From the datasheet:
The TL431 and TL432 devices are three-terminal
adjustable shunt regulators.
It is a very versatile device that one can use as a shunt regulator or a voltage reference or à Zener diode. And more.
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