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TL431

TL431 is an integrated circuit (IC) of a three-output adjustable parallel voltage stabilizer with improved temperature stability. With an external divider, the TL431 is able to stabilize voltages from 2.5 to 36 V at currents up to 100 mA . Typical deviation of the actual value of the reference voltage from the passport value is measured in units of mV, the maximum permissible deviation is several tens of mV . The chip is well suited for controlling powerful transistors ; its use in conjunction with low - voltage MOS transistors allows you to create economical linear stabilizers with a particularly low voltage drop . In the circuitry of pulsed voltage converters, TL431 is the actual industry standard for a stabilizer error amplifier with optocoupler isolation of input and output circuits. .

TL431
Analog integrated circuit
TL 431 symbol and basic structure.png Graphic symbol and functional block diagram
Type ofPrecision parallel voltage regulator
Year of development1977
DeveloperTexas Instruments

TL431 first appeared in Texas Instruments catalogs in 1977 [1] [2] . In the XXI century, TL431 and its functional analogues are produced by many manufacturers in various versions (TL432, ATL431, KA431, LM431, TS431, 142EN19 and others), which differ in crystal topologies , accuracy and frequency characteristics, minimum operating currents and areas of safe operation .

Device and principle of operation

 
Circuit diagram. Voltages at internal nodes are indicated for stabilization mode at U KA = 7 V [3]
 
The dependence of the cathode current on the control voltage in the region of the switching threshold [4]

TL431 - a three-pin threshold element, built on bipolar transistors , is a kind of analog of an ideal transistor with a switching threshold of ≈2.5 V. The “base”, “collector” and “emitter” of TL431 are traditionally referred to as control input (R), cathode (C) and anode (A) respectively. A positive control voltage U ref is applied between the control input and the anode, and the cathode-anode current I KA serves as the output signal [5] .

Functionally, at the level of abstraction, TL431 contains a reference voltage source of ≈2.5 V and an operational amplifier that compares Uref with a reference voltage on a virtual internal node [6] . Physically, both functions are tightly, inextricably integrated in the TL431 input stages. A virtual reference level of ≈2.5 V is not generated at any point in the circuit: the Vidlar bandgap on transistors T3, T4 and T5 is the actual source of the reference voltage, generating voltage ≈1.2 V and optimized for operation in conjunction with emitter repeaters T1 and T6 [7] . The differential amplifier is formed by two counter-connected current sources on transistors T8 and T9: the positive difference between the collector currents T8 and T9, branching into the base T10, controls the output stage [3] . The output stage TL431, which directly controls the load current, is a Darlington transistor of an npn open-collector structure protected by a reverse diode . No protective equipment for overheating or overcurrent is provided [3] [8] .

If U ref does not exceed the switching threshold, then the output stage is closed, and the cascades controlling it consume at rest a current with a typical value of 100 ... 200 μA . With the approach of U ref to the switching threshold, the current consumed by the control stages reaches a value of the order of 300 ... 500 μA , while the output stage remains closed. After exceeding the threshold, the output stage smoothly opens, I KA increases with a slope of approximately 30 mA / V [9] . When U ref exceeds the threshold by about 3 mV , and I KA reaches about 500 ... 600 μA , the steepness rises stepwise to about 1 A / V [9] . With the achievement of the nominal slope, the typical value of which is 1 ... 1.4 A / V , the circuit enters the stabilization mode [9] , in which it behaves like a classical differential voltage to current converter [10] . The current growth stops when the control voltage is stabilized by the action of the negative feedback loop connected between the cathode and the control input [4] [11] . The steady-state value U ref ≈ 2.5 V is called the reference value (U REF ) [11] . In a less common relay mode (comparator mode), the OOS loop is absent, and the current growth is limited only by the characteristics of the power source and load [8] .

The stabilizers on the TL431 are designed so that the microcircuit always works in an active mode with high slope; for this, I KA must not fall below 1 mA [5] [4] [12] . From the point of view of the stability of the control loop, it may be appropriate to increase the minimum current even more, to 5 mA [13] , but in practice this contradicts the requirements for the economizer of the stabilizer [4] . The flowing current of the control input I ref in all modes is approximately constant, its typical value is 2 μA . The manufacturer recommends that the TL431 input circuit be designed in such a way as to guarantee an I ref of at least 4 μA ; operation of the microcircuit with a “hanging” control input is not allowed [14] [8] . An open or short to ground of any of the terminals, as well as a short circuit to any two terminals, cannot destroy TL431, but render the device as a whole inoperative [15] .

Accuracy Specifications

 
The dependence of the reference voltage on temperature. Acceptable intervals of technological variation and temperature drift for the least accurate version with an initial deviation of ± 2% [16]

The rated value of the reference voltage U REF = 2.495 V is determined and tested by the manufacturer at a cathode current of 10 mA , the control input closes to the cathode and the ambient temperature is +25 ° C [14] [17] . The switching threshold (point B on the transfer characteristic) and the threshold for switching to high steepness mode (point C) are not standardized [9] . The actual reference voltage, which sets a specific instance of TL431 in a particular circuit, can be more and less than the passport, depending on four factors:

  • Technological scatter . The permissible spread U REF under normal conditions is for the various TL431 series not more than ± 0.5%, not more than ± 1% or not more than ± 2% [5] ;
  • Temperature drift . The dependence of the bandgap voltage reference on temperature has the shape of a smooth hump. If the characteristics of a specific microcircuit exactly correspond to the design calculation, then the peak of the hump is observed at a temperature of about + 25 ° C, and U REF under normal conditions is exactly equal to 2.495 V ; above and below + 25 ° С, U REF gradually decreases by several mV. For microcircuits with a noticeable deviation of the characteristics from the calculated humps, it shifts in the region of high or low temperatures, and the dependence itself can take on a monotonically decreasing or monotonically increasing character. The deviation of the actual U REF from the passport 2,495 V in all cases does not exceed several tens of mV [18] [16] ;
  • Effect of voltage anode-cathode (U KA ). With increasing U KA, the reference voltage TL431, necessary to maintain a fixed cathode current, decreases with a typical speed of 1.4 mV / V (but not more than 2.7 mV / V ) [17] . The reciprocal of this indicator, approximately 300 ... 1000 ( 50 ... 60 dB ), is the upper limit of the voltage gain in the low-frequency region [19] ;
  • The effect of cathode current . With increasing cathode current, ceteris paribus, U REF increases with a speed of about 0.5 ... 1 mV / mA , which corresponds to a steepness of conversion of 1 ... 2 A / V [10] [9] .

Frequency Response

The amplitude-frequency characteristic (AFC) of TL431, compensated by the built-in Miller capacitance of the output stage [8] , is described to a first approximation by the first-order low-pass filter equation; The simplest frequency-dependent circuit model consists of an ideal voltage-to-current converter, the output of which is shunted by a capacitance of 70 nF [19] . When working on a typical resistive load with a resistance of 230 Ohms, the decay of the frequency response of the standard TL431 begins at around 10 kHz [19] , and the calculated unit gain frequency, independent of the load resistance, is about 2 MHz [20] . Due to second-order phenomena, the frequency response in the higher frequency region decreases faster than the model predicts, so the real unit gain frequency is only 1 MHz ; in practice, this difference does not matter [20] .

Rise and fall rates I KA , U KA and settling time U REF are not standardized. According to Texas Instruments, when the power is turned on, U KA quickly increases to ≈2 V and, temporarily, by about 1 μs , stops at this level. Then, for about 0.5 ... 1 μs , the built-in capacitor charges, and a constant stabilized U KA is established at the cathode [21] .

Shunting the anode and cathode of a TL431 capacitor can lead to self-excitation [22] . With small (not more than 1 nF ) and large (over 10 μF ) capacitances, TL431 is stable; in the region of 1 nF ... 10 μF, self-excitation is likely [23] [24] . The width of the instability region depends on the combination of I KA and U KA . The worst in terms of stability is the combination of low currents and low voltages; on the contrary, at high currents and voltages, when the power dissipated by the microcircuit approaches the limit value, TL431 becomes absolutely stable [25] . However, even a relatively high voltage stabilizer can self-excite when turned on, when the voltage at the cathode has not yet risen to the standard level [23] .

The schedules of the boundary stability conditions published in the technical documentation [14] are, according to Texas Instruments itself , unjustifiably optimistic [25] . They describe a “typical” microcircuit with a zero , while in practice one should focus on a phase margin of at least 30 ° [25] . To suppress self-excitation, it is usually sufficient to include between the anode of TL431 and the load capacitance an “anti-ring” resistance of 1 ... 1,000 Ohms ; its minimum value is determined by the combination of the load capacity, I KA and U KA [26] .

Application

Linear Voltage Regulators

 
Basic configurations of linear stabilizers on TL431. RB is the ballast resistance, RA is the anti-chime resistance isolating the TL431 cathode from the gate capacity of the MOS transistor, ΔU is an additional gate power source

In the simplest circuit of a parallel voltage stabilizer, the control input TL431 is closed to the cathode, which turns the microcircuit into a functional analog of a zener diode with a fixed reference voltage of ≈2.5 V. Typical internal resistance of such a "zener diode" at frequencies up to 100 kHz is approximately 0.2 ohms ; in the frequency range 100 kHz ... 10 MHz, it monotonically increases to about 10 ohms [27] . To stabilize higher voltages, the control input TL431 is connected to a resistive divider R2R1 connected between the cathode and anode. The stabilized voltage of the anode-cathode and the internal resistance of such a "zener diode" increase in(one+R2/Rone) {\ displaystyle (1 + R2 / R1)}   times [28] . The maximum allowable stabilization voltage should not exceed +36 V , the maximum allowable voltage at the cathode is limited to +37 V [29] . Initially, it was this inclusion of the TL431 that was the main one: the microcircuit was positioned on the market as an economical alternative to expensive precision zener diodes [30] .

The addition of a parallel stabilizer circuit with an emitter follower included in the feedback loop turns it into a series stabilizer. Conventional or compound transistors of the npn structure, used as through valves, are operable only at a sufficiently high voltage drop between the input and output, which reduces the efficiency of the stabilizer [31] . Transistors of the pnp structure in saturation mode are operable at collector-emitter voltages up to ≈0.25 V , but at the same time they require high control currents, which forces the use of composite transistors with a minimum voltage drop of 1 V or higher [31] . The smallest voltage drop is achieved when using high - power MOS transistors [31] . Stabilizers with source repeaters are schematically simple, stable, economical, but require an additional power source for the shutters of MOS transistors (ΔU in the illustration) [31] .

Switching Voltage Regulators

 
Typical TL431 switching in a switching voltage regulator [32] [33]
 
Precision source [34] and current limiter [35]

The TL431, loaded on an optocoupler LED , is the actual industry standard for the error amplifier in household switching voltage converters [10] [12] [11] . The voltage divider R1R2, which sets the voltage at the control input of TL431, and the cathode of the LED are connected to the output of the converter, and the optocoupler phototransistor is connected to the control input of the PWM controller of its primary circuit. In order to ensure that the minimum cathode current TL431 does not fall below 1 mA , the optocoupler LED is shunted by a resistor R3 of the order of 1 kΩ [4] [36] . For example, in a typical switching notebook power supply, according to 2012, the average I KA is 1.5 mA , of which 0.5 mA flows through the LED, and 1 mA through the shunt [4] .

Designing effective but stable frequency compensation circuits for such stabilizers is not an easy task [37] . In the simplest configuration, compensation is assigned to the C1R4 integrating circuit [37] . In addition to this circuit, the output smoothing filter of the converter and the microcircuit itself, another frequency-dependent link is implicitly present in the circuit, with a cutoff frequency of the order of 10 kHz — the output capacitance of the phototransistor in conjunction with the resistance of its collector load [38] . In this case, two feedback loops are simultaneously closed through the microcircuit: the main, slow loop is closed through a divider to the TL431 control input; secondary, fast ( English fast lane ) is closed via an LED to the TL431 cathode [39] . A fast loop can be broken, for example, by fixing the voltage at the cathode of the LED with a Zener diode [40] or by connecting the cathode of the LED to a separate filter [41] .

Voltage Comparators

 
The basic configuration of a comparator with a fixed switching threshold and its derivatives are the simplest time relay and voltage monitor with a cascade connection of two comparators

The simplest comparator circuit on TL431 requires a single resistor that limits the cathode current limit to a recommended level of 5 mA [42] . Smaller values ​​are possible, but undesirable due to the delay of switching time from open (logical zero) to closed (logical unit) state [42] . The switching time from closed to open depends on the excess of U ref over the switching threshold: the larger the excess, the faster the comparator is triggered. The optimal switching speed is achieved with a ten percent excess, while the output resistance of the signal source should not exceed 10 kOhm [42] . In a fully open state, U KA drops to 2 V , which is consistent with TTL and CMOS levels at supply voltages of 5 V and higher [43] . To match TL431 with low-voltage CMOS logic, you must use an external voltage divider [43] or replace TL431 with an analog chip with a lower switching threshold, for example TLV431 [44] .

Comparators and logic inverters on TL431 are easily interconnected according to the principles of relay logic . For example, in the above voltage monitor circuit, the output stage opens, and the output signal takes a logical zero value if, and only if, the input voltage U BX falls within the interval

UREF(one+R3/Rfour)<UBX<UREF(one+Rone/R2){\ displaystyle U_ {REF} (1 + R3 / R4) <U_ {BX} <U_ {REF} (1 + R1 / R2)}   [45] .

The circuit is operational if the conditionRone/R2>R3/Rfour {\ displaystyle R1 / R2> R3 / R4}   performed with a sufficient margin [45] .

Undocumented Modes

The amateur radio press has repeatedly published designs of low-frequency voltage amplifiers on the TL431, which are usually unsuccessful [46] . In an effort to suppress the nonlinearity of the microcircuit, the designers increased the feedback depth and thereby reduced the gain to unreasonably low values [46] . Stabilization of the mode of operation of amplifiers on the TL431 also proved to be a difficult task [46] .

The self-excitation tendency of TL431 can be used to construct a generator controlled by voltage at frequencies from several kHz to 1.5 MHz [47] . The frequency range of such a generator and the nature of the dependence of the frequency on the control voltage strongly depend on the TL431 series used: microcircuits of the same name from different manufacturers in this undocumented mode are not interchangeable [47] . The TL431 pair can also be used in an astable multivibrator circuit at frequencies from fractions of Hz to about 50 kHz [48] . In this circuit, TL431 also operate in an undocumented mode: the charge currents of the timing tanks flow through the diodes protecting the control inputs (T2 in the circuit diagram) [48] .

Non-standard options and functional analogues

 
Micrographs of TL431 crystals from three different manufacturers on the same scale. The largest bright area of ​​each crystal is the frequency compensation capacitance, the large comb structure next to it is the output transistor, the groups of “extra” contact pads are the technological contacts for step adjustment at the manufacturer

Microchips of various manufacturers, produced under the name TL431 or under close names (KA431, TS431, etc.), may differ significantly from the original TL431 manufactured by Texas Instruments. Sometimes differences are revealed only empirically, when testing IP in undocumented modes [47] ; sometimes they are explicitly declared in the manufacturers documentation. So, Vishay's TL431 is characterized by an anomalously high, about 75 dB , voltage gain at low frequencies [19] . The decrease in the gain of this IP begins at around 100 Hz [19] . In the frequency range above 10 kHz, the frequency response of TL431 Vishay is approaching the standard; the unit gain frequency, about 1 MHz , coincides with the standard one [19] . The SG6105 PWM controller microcircuit contains two independent stabilizers declared as exact analogs of the TL431, but their maximum permissible I KA and U KA are only 16 V and 30 mA ; the accuracy characteristics of these stabilizers are not tested by the manufacturer [49] .

The TL430 microcircuit is a historical functional analogue of the TL431 with a voltage reference of 2.75 V and a maximum permissible cathode current of 150 mA , manufactured by Texas Instruments only in a housing for mounting in holes [50] . The TL430 built-in bandgap, unlike the simultaneously released TL431, was not temperature compensated and was less accurate; there was no protective diode in the TL430 output stage [51] . Launched in the XXI century, the TL432 chip is a conventional TL431 crystals, packed in surface mount housings with non-standard pinout [52] .

In 2015, Texas Instruments announced the release of ATL431 - a functional analogue of TL431, optimized for operation in economical switching stabilizers [53] . The recommended minimum cathode current of ATL431 is only 35 μA versus 1 mA for standard TL431 with the same limit values ​​of cathode current ( 100 mA ) and anode-cathode voltage ( 36 V ) [54] . The unit gain frequency is shifted down to 250 kHz to suppress high-frequency noise gain [54] . The graphs of the boundary stability conditions also have a completely different look: at low currents and a voltage of 15 V anode-cathode, the circuit is absolutely stable at any load capacitance, provided that high-quality low - inductance capacitors are used [55] [56] . The minimum recommended resistance of the “anti-ring” resistor is 250 Ohms versus 1 Ohm for the standard TL431 [57] .

In addition to the TL431 family of microcircuits, as of 2015, only two integrated circuits of parallel stabilizers were widely used, having a fundamentally different circuitry, reference levels, and ultimate operating characteristics [58] :

  • The bipolar IC LMV431 manufactured by Texas Instruments has a reference voltage of 1.24 V and is able to stabilize voltages up to 30 V at a cathode current of 80 μA to 30 mA [59] [60] ;
  • The low-voltage CMOS microcircuit NCP100 manufactured by On Semiconductor has a reference voltage of 0.7 V and is able to stabilize voltages up to 6 V at a cathode current of 100 μA to 20 mA [61] [62] .

The circuitry of devices on the LMV431 and NCP100 is similar to the circuitry of devices on the TL431 [58] .

Notes

  1. ↑ The voltage regulator handbook / ed. JD Spencer, DE Pippinger. - Texas Instruments, 1977 .-- P. 82, 86, 132. - 198 p. - ISBN 9780895121011 .
  2. ↑ The first technical documentation for the serial TL431 is dated July 1978. See TL431, TL431A Precision Shunt Regulators // Texas Instruments Datasheet. - 1999 .-- July ( no. SLVS005J ).
  3. ↑ 1 2 3 Basso, 2012 , p. 384.
  4. ↑ 1 2 3 4 5 6 Basso, 2012 , p. 388.
  5. ↑ 1 2 3 Texas Instruments, 2015 , p. nineteen.
  6. ↑ Texas Instruments, 2015 , p. 20: "virtual internal pin".
  7. ↑ Basso, 2012 , pp. 383, 385-386.
  8. ↑ 1 2 3 4 Texas Instruments, 2015 , p. 20.
  9. ↑ 1 2 3 4 5 Basso, 2012 , p. 387.
  10. ↑ 1 2 3 Basso, 2012 , p. 383.
  11. ↑ 1 2 3 Zhanyou Sha, 2015 , p. 154.
  12. ↑ 1 2 Brown, 2001 , p. 78.
  13. ↑ Tepsa, Suntio, 2013 , p. 93.
  14. ↑ 1 2 3 Integrated Circuits, 1996 , p. 221.
  15. ↑ Zamora, Marco. TL431 Pin FMEA (English) // Texas Instruments Application Report. - 2018 .-- January ( no. SNVA809 ). - P. 4.
  16. ↑ 1 2 Texas Instruments, 2015 , p. 14.
  17. ↑ 1 2 Texas Instruments, 2015 , pp. 5-13.
  18. ↑ Camenzind, 2005 , pp. 7-5, 7-6, 7-7.
  19. ↑ 1 2 3 4 5 6 Tepsa, Suntio, 2013 , p. 94.
  20. ↑ 1 2 Schönberger, 2012 , p. four.
  21. ↑ Texas Instruments, 2015 , p. 25.
  22. ↑ Michallick, 2014 , p. one.
  23. ↑ 1 2 TS431 Adjustable Precision Shunt Regulator // Taiwan Semiconductor Datasheet. - P. 3.
  24. ↑ Michallick, 2004 , p. 2.
  25. ↑ 1 2 3 Michallick, 2014 , p. 2.
  26. ↑ Michallick, 2014 , pp. 3-4.
  27. ↑ Texas Instruments, 2015 , pp. 5-13, 16.
  28. ↑ Texas Instruments, 2015 , p. 24.
  29. ↑ Texas Instruments, 2015 , p. four.
  30. ↑ Texas Instruments, 1985 , p. 6.22.
  31. ↑ 1 2 3 4 Dubhashi A. AN-970. Power field effect transistors in linear stabilizers with a small voltage drop // Power semiconductor devices / Translated from English by V.V. Tokarev. - Voronezh: LLP MP Elist, 1995. - S. 375-376.
  32. ↑ Basso, 2012 , p. 393.
  33. ↑ Ridley, 2015 , pp. 12.
  34. ↑ Texas Instruments, 2015 , p. 29.
  35. ↑ Texas Instruments, 2015 , p. 28.
  36. ↑ Basso, 2012 , p. 392.
  37. ↑ 1 2 Ridley, 2015 , p. 2.
  38. ↑ Ridley, 2015 , p. 3.
  39. ↑ Basso, 2012 , pp. 396–397.
  40. ↑ Basso, 2012 , pp. 397–398.
  41. ↑ Ridley, 2015 , p. four.
  42. ↑ 1 2 3 Texas Instruments, 2015 , p. 22.
  43. ↑ 1 2 Texas Instruments, 2015 , p. 23.
  44. ↑ Rivera-Matos, 2018 , p. one.
  45. ↑ 1 2 Rivera-Matos, 2018 , p. 3
  46. ↑ 1 2 3 Field I. Electret Mic Booster // Elektor. - 2010. - No. 7 . - P. 65-66.
  47. ↑ 1 2 3 Ocaya RO VCO using the TL431 reference // EDN Network. - 2013 .-- October ( no. 10 ).
  48. ↑ 1 2 Clements G. TL431 Multivibrator // Elektor. - 2009. - No. July / August . - P. 40-41.
  49. ↑ SG6105 Power Supply Supervisor + Regulator + PWM (Eng.) // System General Product Specification. - 2004 .-- 7 July. - P. 1, 5, 6.
  50. ↑ TL430 Adjustable Shunt Regulator ( Texas ) // Texas Instruments Datasheet. - 2005. - January ( no. SLVS050D ).
  51. ↑ Texas Instruments, 1985 , p. 6.21.
  52. ↑ Texas Instruments, 2015 , p. one.
  53. ↑ Leverette, 2015 , p. 2.
  54. ↑ 1 2 Leverette, 2015 , p. 3.
  55. ↑ Leverette, 2015 , p. four.
  56. ↑ Texas Instruments, 2016 , pp. 7, 8.
  57. ↑ Texas Instruments, 2016 , p. 17.
  58. ↑ 1 2 Zhanyou Sha, 2015 , p. 153.
  59. ↑ Zhanyou Sha, 2015 , p. 157.
  60. ↑ LMV431x Low-Voltage (1.24-V) Adjustable Precision Shunt Regulators ( unspecified ) . Texas Instruments (2014).
  61. ↑ Zhanyou Sha, 2015 , p. 155.
  62. ↑ NCP100: Sub 1.0 V Precision Adjustable Shunt Regulator ( unspecified ) . On Semiconductor (2009).

Literature

  • Integrated circuits. Microchips for linear power supplies and their application. - M .: Dodeca, 1996 .-- ISBN 5878350211 .
  • Basso C. Chapter 7. TL431-based Compensators // Designing Control Loops for Linear and Switching Power Supplies . - Artech House, 2012 .-- P. 383–454. - ISBN 9781608075577 .
  • Brown M. Power Supply Cookbook . - Newnes. - 2001. - (EDN Series for Design Engineers). - ISBN 9780080480121 .
  • Camenzind H. Designing Analog Circuits . - Virtualbookworm Publishing, 2005 .-- 244 p. - ISBN 9781589397187 .
  • Leverette A. Designing with the "Advanced" TL431, ATL431 (Eng.) // Texas Instruments Application Report. - 2015 .-- June ( no. SLVA685 ). - P. 1-7.
  • Michallick R. Understanding Stability Boundary Conditions Charts in TL431, TL432 Data Sheet // Texas Instruments Application Report. - 2014 .-- January ( no. SLVA482A ). - P. 1-6.
  • Ridley R. Designing with the TL431 - the first complete analysis // Switching Power Magazine. - 2008 .-- 1 August. - P. 1-5.
  • Ridley R. Using the TL431 in a Power Supply // Power Systems Design Europe. - 2007. - June. - P. 16-18.
  • Rivera-Matos R. and Than E. Using the TL431 as a Voltage Comparator // Texas Instruments Application Report. - 2018 .-- January ( no. SLVA987 ). - P. 1-4.
  • Schönberger J. Design of a TL431-Based Controller for a Flyback Converter . - Plexim GMBH, 2012.
  • Tepsa T., Suntio T. Adjustable Shunt Regulator Based Control Systems // IEEE Power Electronics Letters. - 2013 .-- Vol. 1. - P. 93–96.
  • Linear and Interface Circuit Application. Volume I: Amplifiers, Comparators, Timers, Voltage Regulators / Ed. DE Pippinger and EJ Tobaben. - Texas Instruments, 1985.
  • TL43xx Precision Programmable Reference // Texas Instruments Datasheet. - 2015 .-- January ( no. SLVS543O ).
  • ATL431, ATL432 2.5-V Low Iq Adjustable Precision Shunt Regulator (Eng.) // Texas Instruments Datasheet. - 2016. - October ( no. SLVSCV5D ).
  • Zhanyou Sha et al. Optimal Design of Switching Power Supply . - Wiley, 2015 .-- ISBN 9781118790946 .
Source - https://ru.wikipedia.org/w/index.php?title=TL431&oldid=101409711


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