TL431 is a three terminal adjustable shunt reference voltage source with good thermal stability. Its output voltage can be arbitrarily set to any value from the Vref (2.5V) to the 36V range with two resistors. The typical dynamic impedance of the device is 0.2 ohms, you can use it instead of Zener diodes in many applications such as digital voltmeter, amplifier circuit, adjustable voltage power supply, switching power supply etc..
Characteristic：
Programmable output voltage is 36V
Voltage reference error: + 0.4%, typical value @25 C (TL431B)
Low dynamic output impedance, typical 0.22
Load current capacity to 100mA 1.0mA
Equivalent full range temperature coefficient 50 ppm/
Temperature compensation operation full rated operating temperature range
Low output noise voltage


　　                         Figure 1 TO92 package pin diagram

　　                          Figure 28 pin package pin function

　　                Figure 3 SOP-8 patch package pin diagram


　                     Figure 4 TL431 symbols and internal block diagram



　                                                  　Figure 5 TL431 internal circuit diagram

　　MAXIMUM RATINGS (Full operating ambient temperature range applies, unlessotherwise noted.)
最大額定值（環境溫度范圍適用，除非另有說明。 ）

Rating 參數		Symbol 符號	數值	Unit 單位
Cathode to Anode Voltage陰極陽極電壓		VKA	37	V
Cathode Current Range, Continuous 陰極電流范圍，連續		IK	–100 to +150	mA
Reference Input Current Range, Continuous 參考輸入電流范圍，連續		Iref	–0.05 to +10	mA
OperatingJunctionTemperature工作結溫		TJ	150	℃
Operating Ambient Temperature Range 操作環境溫度范圍	TL431I,TL431AI, TL431BI	TA	–40 to +85	℃
	TL431C, TL431AC, TL431BC		0 to +70
StorageTemperature Range儲存溫度范圍		Tstg	–65 to +150	℃
Total Power Dissipation總耗散功率 常溫@ TA = 25℃ Derate above 25℃ Ambient Temperature	D, LP后綴塑封	PD	0.70	W
	P后綴塑封		1.10
	DM 后綴塑封		0.52
Total Power Dissipation @ TC = 25℃ Derate above 25℃ Case Temperature 總耗散功率 外殼溫度	D, LP后綴塑封	PD	1.5	W
	P后綴塑封		3.0

　　RECOMMENDED OPERATING CONDITIONS建議操作條件


　　ELECTRICAL CHARACTERISTICS(TA=25℃, unless otherwise noted.)電氣特性（25℃ ，除非另有說明。）


　　ELECTRICAL CHARACTERISTICS (TA = 25℃, unless otherwise noted.)電氣特性（25℃，除非另有說明。）



　　Figure 6 test circuitVKA = Vref                   Figure 7test circuitVKA > Vref                                                       Figure 8test circuit  for Ioff

　　Diagram：

                 Fig. 9 cathode current and cathode voltage                                        Fig. 10 cathode current and cathode voltage



  　Fig. 11 reference input voltage and ambient temperature                  Fig. 12 reference input current and ambient temperature



   Fig. 13 variation of the reference input voltage with the cathode voltage      Figure 14 off state cathode current with ambient temperature



　　       FIG. 15 dynamic impedance and frequency                                FIG. 16 dynamic impedance with ambient temperature



　       Fig. 17 open loop voltage gain and frequency                                         Fig. 18 spectral noise density


　　                              Fig. 19 impulse response                                            Figure 20 stability boundary conditions

　　Application method:


The stability of the B, C, and D boundary conditions of the test circuit for the stability diagram of the curve a boundary conditions are tested.

     Fig. 23 circuit diagram of shunt regulator           Fig. 24 current shunt regulator circuit

Figure 25 control three end fixed voltage stabilizing output circuit   Figure 26 series voltage regulation circuit     Fig. 27 overvoltage protection circuit


Fig. 28 circuit of constant current source    Fig. 29 constant current source circuit    Fig. 30 bidirectional thyristor overvoltage protection circuit

            Fig. 31 voltage monitor circuit                 Fig. 32 comparison of single power supply and temperature compensation circuit


                Fig. 33 circuit diagram of linear ohm meter                   Figure 34 simple 400 MW phono amplifier circuit


                  Figure 35 high efficiency buck switching converter circuit



                                                              Fig. 36 simplified TL431 device model



                                                                 Figure 37 package diagram


                       Figure 38 SOP-8 patch package



                                             Figure 39 package diagram