TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 D D D D D D Equivalent Full-Range Temperature Coefficient . . . 30 ppm/°C 0.2-Ω Typical Output Impedance Sink-Current Capability . . . 1 mA to 100 mA Low Output Noise Adjustable Output Voltage . . . Vref to 36 V Available in a Wide Range of High-Density Packages description The TL431 and TL431A are three-terminal adjustable shunt regulators with specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V with two external resistors (see Figure 17). These devices have a typical output impedance of 0.2 Ω. Active output circuitry provides a very sharp turn-on characteristic, making these devices excellent replacements for Zener diodes in many applications, such as onboard regulation, adjustable power supplies, and switching power supplies. D PACKAGE (TOP VIEW) CATHODE ANODE ANODE NC 1 8 2 7 3 6 4 5 REF ANODE ANODE NC P OR PW PACKAGE (TOP VIEW) CATHODE NC NC NC 1 8 2 7 3 6 4 5 REF NC ANODE NC NC – No internal connection PK PACKAGE (TOP VIEW) REF ANODE CATHODE The TL431C and TL431AC are characterized for operation from 0°C to 70°C, and the TL431I and TL431AI are characterized for operation from –40°C to 85°C. LP PACKAGE (TOP VIEW) CATHODE ANODE REF KTP PACKAGE (TOP VIEW) CATHODE ANODE ANODE REF Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Copyright 1999, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 AVAILABLE OPTIONS PACKAGED DEVICES SMALL OUTLINE (D) PLASTIC FLANGE MOUNT (KTP) TO-226AA (LP) PLASTIC DIP (P) SOT-89 (PK) SHRINK SMALL OUTLINE (PW) 0°C to 70°C TL431CD TL431ACD TL431CKTPR TL431CLP TL431ACLP TL431CP TL431ACP TL431CPK TL431CPW –40°C to 85°C TL431ID TL431AID TL431ILP TL431AILP TL431IP TL431AIP TL431IPK TA CHIP FORM (Y) TL431Y The D and LP packages are available taped and reeled. The KTP and PK packages are only available taped and reeled. Add the suffix R to device type (e.g., TL431CDR). Chip forms are tested at TA = 25°C. symbol REF ANODE CATHODE functional block diagram CATHODE + REF _ Vref ANODE equivalent schematic† CATHODE 800 Ω 800 Ω 20 pF REF 150 Ω 3.28 kΩ 2.4 kΩ 7.2 kΩ 4 kΩ 20 pF 1 kΩ 800 Ω ANODE † All component values are nominal. 2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 10 kΩ TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 absolute maximum ratings over operating free-air temperature range (unless otherwise noted)† Cathode voltage, VKA (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 V Continuous cathode current range, IKA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –100 mA to 150 mA Reference input current range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –50 µA to 10 mA Package thermal impedance, θJA (see Notes 2 and 3): D package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97°C/W LP package . . . . . . . . . . . . . . . . . . . . . . . . . . 156°C/W KTP package . . . . . . . . . . . . . . . . . . . . . . . . . 28°C/W P package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127°C/W PK package . . . . . . . . . . . . . . . . . . . . . . . . . . . 52°C/W PW package . . . . . . . . . . . . . . . . . . . . . . . . . . 149°C/W Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds: D, P, or PW package . . . . . . . . . . . . 260°C Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds: LP or PK package . . . . . . . . . . . . . . 300°C Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C † Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. NOTES: 1. Voltage values are with respect to the anode terminal unless otherwise noted. 2. Maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any allowable ambient temperature is PD = (TJ(max) – TA)/θJA. Operating at the absolute maximum TJ of 150°C can impact reliability. 3. The package thermal impedance is calculated in accordance with JESD 51, except for through-hole packages, which use a trace length of zero. recommended operating conditions Cathode voltage, VKA Cathode current, IKA TL431C, TL431AC free air temperature range, range TA Operating free-air TL431I, TL431AI POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 MIN MAX Vref 1 36 UNIT V 100 mA 0 70 –40 85 °C 3 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise noted) TEST CIRCUIT PARAMETER TEST CONDITIONS IKA = 10 mA TL431C UNIT MIN TYP MAX 2440 2495 2550 mV 4 25 mV –1.4 –2.7 –1 –2 mV V Vref Reference voltage 2 VKA = Vref, VI(dev) Deviation of reference voltage over full temperature range (see Figure 1) 2 VKA = Vref, IKA = 10 mA, TA = full range† DVref DVKA Ratio of change g in reference voltage g to the change in cathode voltage 3 IKA = 10 mA Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA II(dev) Deviation of reference current over full temperature range (see Figure 1) 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞, TA = full range† 0.4 1.2 µA Imin Minimum cathode current for regulation 2 VKA = Vref 0.4 1 mA Ioff Off-state cathode current 4 0.1 1 µA |zKA| Dynamic impedance (see Figure 1) 1 VKA = 36 V, Vref = 0 IKA = 1 mA to 100 mA, VKA = Vref, f ≤ 1 kHz 0.2 0.5 Ω ∆VKA = 10 V – Vref ∆VKA = 36 V – 10 V † Full range is 0°C to 70°C for the TL431C. The deviation parameters Vref(dev) and Iref(dev) are defined as the differences between the maximum and minimum values obtained over the recommended temperature range. The average full-range temperature coefficient of the reference voltage, αVref, is defined as: Ťa Ť ǒ Vref ppm °C ǒ Ǔ Ǔ + V I(dev) V at 25°C ref DTA Maximum Vref 10 6 VI(dev) Minimum Vref ∆TA where: ∆TA is the recommended operating free-air temperature range of the device. αVref can be positive or negative, depending on whether minimum Vref or maximum Vref, respectively, occurs at the lower temperature. Example: maximum Vref = 2496 mV at 30°C, minimum Vref = 2492 mV at 0°C, Vref = 2495 mV at 25°C, ∆TA = 70°C for TL431C Ť Ť+ǒ aVref Ǔ 4 mV 2495 mV 70°C 10 6 [ 23 ppmń°C Because minimum Vref occurs at the lower temperature, the coefficient is positive. Calculating Dynamic Impedance Ť Ť + DD V KA I KA When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit is given by: The dynamic impedance is defined as: z KA Ť Ťǒ Ǔ Ȁ + DDVI [ zKA 1 ) R1 R2 |z | Figure 1. Calculating Deviation Parameters and Dynamic Impedance 4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise noted) PARAMETER TEST CIRCUIT TEST CONDITIONS IKA = 10 mA TL431I UNIT MIN TYP MAX 2440 2495 2550 mV 5 50 mV –1.4 –2.7 –1 –2 mV V Vref Reference voltage 2 VKA = Vref, VI(dev) Deviation of reference voltage over full temperature range (see Figure 1) 2 VKA = Vref, IKA = 10 mA, TA = full range† DVref DVKA Ratio of change g in reference voltage g to the change in cathode voltage 3 IKA = 10 mA Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA II(dev) Deviation of reference current over full temperature range (see Figure 1) 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞, TA = full range† 0.8 2.5 µA Imin Minimum cathode current for regulation 2 VKA = Vref 0.4 1 mA Ioff Off-state cathode current 4 0.1 1 µA |zKA| Dynamic impedance (see Figure 1) 2 VKA = 36 V, Vref = 0 IKA = 1 mA to 100 mA, VKA = Vref, f ≤ 1 kHz 0.2 0.5 Ω ∆VKA = 10 V – Vref ∆VKA = 36 V – 10 V † Full range is –40°C to 85°C for the TL431I. electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise noted) PARAMETER TEST CIRCUIT TEST CONDITIONS IKA = 10 mA TL431AC UNIT MIN TYP MAX 2470 2495 2520 mV 4 25 mV –1.4 –2.7 –1 –2 mV V Vref Reference voltage 2 VKA = Vref, VI(dev) Deviation of reference voltage over full temperature range (see Figure 1) 2 VKA = Vref, IKA = 10 mA, TA = full range† DVref DVKA Ratio of change g in reference voltage g to the change in cathode voltage 3 IKA = 10 mA Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA II(dev) Deviation of reference current over full temperature range (see Figure 1) 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞, TA = full range‡ 0.8 1.2 µA Imin Minimum cathode current for regulation 2 VKA = Vref 0.4 0.6 mA Ioff Off-state cathode current 4 0.1 0.5 µA |zKA| Dynamic impedance (see Figure 1) 1 VKA = 36 V, Vref = 0 IKA = 1 mA to 100 mA, VKA = Vref, f ≤ 1 kHz 0.2 0.5 Ω ∆VKA = 10 V – Vref ∆VKA = 36 V – 10 V ‡ Full range is 0°C to 70°C for the TL431AC. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise noted) TEST CIRCUIT PARAMETER TEST CONDITIONS IKA = 10 mA TL431AI UNIT MIN TYP MAX 2470 2495 2520 mV 5 50 mV –1.4 –2.7 –1 –2 mV V Vref Reference voltage 2 VKA = Vref, VI(dev) Deviation of reference voltage over full temperature range (see Figure 1) 2 VKA = Vref, IKA = 10 mA, TA = full range† DVref DVKA Ratio of change g in reference voltage g to the change in cathode voltage 3 IKA = 10 mA Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA II(dev) Deviation of reference current over full temperature range (see Figure 1) 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞, TA = full range† 0.8 2.5 µA Imin Minimum cathode current for regulation 2 VKA = Vref 0.4 0.7 mA Ioff Off-state cathode current 4 0.1 0.5 µA |zKA| Dynamic impedance (see Figure 1) 2 VKA = 36 V, Vref = 0 IKA = 1 mA to 100 mA, VKA = Vref, f ≤ 1 kHz 0.2 0.5 Ω ∆VKA = 10 V – Vref ∆VKA = 36 V – 10 V † Full range is –40°C to 85°C for the TL431AI. electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise noted) TEST CIRCUIT PARAMETER Vref Reference voltage 2 TEST CONDITIONS VKA = Vref, TL431Y MIN TYP MAX IKA = 10 mA ∆VKA = 10 V – Vref 2495 mV –1.4 –1 mV V 2 µA DVref DVKA Ratio of change g in reference voltage g to the change in cathode voltage 3 Iref Reference input current 3 ∆VKA = 36 V – 10 V IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ Imin Minimum cathode current for regulation 2 VKA = Vref 0.4 mA Ioff Off-state cathode current 4 0.1 µA |zKA| Dynamic impedance‡ 2 VKA = 36 V, Vref = 0 IKA = 1 mA to 100 mA, VKA = Vref, f ≤ 1 kHz 0.2 Ω ‡ Calculating dynamic impedance: IKA = 10 mA Ť Ť + DD V KA I KA When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit is given by: The dynamic impedance is defined as: z KA [ |z Ȁ + ∆V ∆I |z | 6 UNIT KA ǒ) Ǔ | 1 R1 R2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 PARAMETER MEASUREMENT INFORMATION VKA Input IKA Vref Figure 2. Test Circuit for VKA = Vref Input VKA IKA R1 Iref R2 Vref V KA +V ǒ ) Ǔ) ref 1 R1 R2 I ref R1 Figure 3. Test Circuit for VKA > Vref Input VKA Ioff Figure 4. Test Circuit for Ioff POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 TYPICAL CHARACTERISTICS Table 1. Graphs FIGURE Reference input voltage vs Free-air temperature 5 Reference input current vs Free-air temperature 6 Cathode current vs Cathode voltage 7, 8 Off-state cathode current vs Free-air temperature 9 Ratio of delta reference voltage to change in cathode voltage vs Free-air temperature 10 Equivalent input noise voltage vs Frequency 11 Equivalent input noise voltage over a 10-second period 12 Small-signal voltage amplification vs Frequency 13 Reference impedance vs Frequency 14 Pulse response 15 Stability boundary conditions 16 Table 2. Application Circuits FIGURE 8 Shunt regulator 17 Single-supply comparator with temperature-compensated threshold 18 Precision high-current series regulator 19 Output control of a three-terminal fixed regulator 20 High-current shunt regulator 21 Crowbar circuit 22 Precision 5-V 1.5-A regulator 23 Efficient 5-V precision regulator 24 PWM converter with reference 25 Voltage monitor 26 Delay timer 27 Precision current limiter 28 Precision constant-current sink 29 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 TYPICAL CHARACTERISTICS† REFERENCE VOLTAGE vs FREE-AIR TEMPERATURE REFERENCE CURRENT vs FREE-AIR TEMPERATURE 2600 VKA = Vref IKA = 10 mA 5 R1 = 10 kΩ R2 = ∞ IKA = 10 mA Vref = 2550 mV‡ 2560 2540 I ref – Reference Current – µ A V ref – Reference Voltage – mV 2580 2520 Vref = 2495 mV‡ 2500 2480 2460 Vref = 2440 mV‡ 2440 2420 2400 –75 –50 –25 0 25 50 100 75 4 3 2 1 125 0 –75 TA – Free-Air Temperature – °C –50 ‡ Data is for devices having the indicated value of Vref at IKA = 10 mA, TA = 25°C. –25 Figure 5 50 75 100 125 CATHODE CURRENT vs CATHODE VOLTAGE 150 800 VKA = Vref TA = 25°C VKA = Vref TA = 25°C 100 I KA – Cathode Current – µ A I KA – Cathode Current – mA 25 Figure 6 CATHODE CURRENT vs CATHODE VOLTAGE 125 0 TA – Free-Air Temperature – °C 75 50 25 0 –25 –50 600 Imin 400 200 0 –75 –100 –2 –200 –1 0 2 1 3 –1 VKA – Cathode Voltage – V 0 1 2 3 VKA – Cathode Voltage – V Figure 7 Figure 8 † Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the various devices. POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 TYPICAL CHARACTERISTICS† RATIO OF DELTA REFERENCE VOLTAGE TO DELTA CATHODE VOLTAGE vs FREE-AIR TEMPERATURE OFF-STATE CATHODE CURRENT vs FREE-AIR TEMPERATURE – 0.85 VKA = 36 V Vref = 0 VKA = 3 V to 36 V – 0.95 2 ∆V ref / ∆V KA – mV/V I off – Off-State Cathode Current – µ A 2.5 1.5 1 0.5 0 –75 –1.05 –1.15 –1.25 –1.35 –50 –25 0 25 50 75 100 –1.45 –75 125 –50 –25 0 25 50 75 100 125 TA – Free-Air Temperature – °C TA – Free-Air Temperature – °C Figure 9 Figure 10 EQUIVALENT INPUT NOISE VOLTAGE vs FREQUENCY Vn – Equivalent Input Noise Voltage – nV/ Hz 260 IO = 10 mA TA = 25°C 240 220 200 180 160 140 120 100 10 100 1k 10 k 100 k f – Frequency – Hz Figure 11 † Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the various devices. 10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 TYPICAL CHARACTERISTICS EQUIVALENT INPUT NOISE VOLTAGE OVER A 10-SECOND PERIOD V n – Equivalent Input Noise voltage – µV 6 5 4 3 2 1 0 –1 –2 –3 f = 0.1 to 10 Hz IKA = 10 mA TA = 25°C –4 –5 –6 0 1 2 3 4 5 6 7 8 9 10 t – Time – s 19.1 V 1 kΩ 500 µF 910 Ω 2000 µF VCC TL431 (DUT) 820 Ω + VCC 1 µF TLE2027 AV = 10 V/mV + – 16 kΩ 16 Ω 160 kΩ 16 kΩ 1 µF TLE2027 To Oscilloscope 22 µF – 33 kΩ AV = 2 V/V 0.1 µF 33 kΩ VEE VEE Figure 12. Test Circuit for Equivalent Input Noise Voltage POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 TYPICAL CHARACTERISTICS SMALL-SIGNAL VOLTAGE AMPLIFICATION vs FREQUENCY A V – Small-Signal Voltage Amplification – dB 60 IKA = 10 mA TA = 25°C 50 Output 15 kΩ IKA 232 Ω 40 9 µF + 30 – 8.25 kΩ 20 GND 10 0 1k TEST CIRCUIT FOR VOLTAGE AMPLIFICATION 10 k 100 k 1M 10 M f – Frequency – Hz Figure 13 REFERENCE IMPEDANCE vs FREQUENCY |z KA | – Reference Impedance – Ω 100 IKA = 10 mA TA = 25°C 1 kΩ Output 10 IKA 50 Ω – + GND 1 TEST CIRCUIT FOR REFERENCE IMPEDANCE 0.1 1k 10 k 100 k 1M 10 M f – Frequency – Hz Figure 14 12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 TYPICAL CHARACTERISTICS PULSE RESPONSE 6 TA = 25°C Input Input and Output Voltage – V 5 220 Ω Output 4 Pulse Generator f = 100 kHz 3 50 Ω Output GND 2 TEST CIRCUIT FOR PULSE RESPONSE 1 0 –1 0 1 2 3 4 5 6 7 t – Time – µs Figure 15 STABILITY BOUNDARY CONDITIONS† 100 I KA – Cathode Current – mA 90 80 A VKA = Vref B VKA = 5 V C VKA = 10 V D VKA = 15 Vf 150 Ω TA = 25°C IKA + VBATT CL B – 70 Stable 60 C Stable 50 A TEST CIRCUIT FOR CURVE A 40 30 D IKA 20 10 0 0.001 150 Ω R1 = 10 kΩ CL + 0.01 0.1 1 10 R2 CL – Load Capacitance – µF – † The areas under the curves represent conditions that may cause the device to oscillate. For curves B, C, and D, R2 and V+ were adjusted to establish the initial VKA and IKA conditions with CL = 0. VBATT and CL were then adjusted to determine the ranges of stability. VBATT TEST CIRCUIT FOR CURVES B, C, AND D Figure 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 13 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 APPLICATION INFORMATION R (see Note A) VI(BATT) VO R1 0.1% Vref TL431 VO R2 0.1% ǒ Ǔ + 1 ) R1 V R2 ref RETURN NOTE A: R should provide cathode current ≥1 mA to the TL431 at minimum VI(BATT). Figure 17. Shunt Regulator VI(BATT) VO TL431 Von ≈ 2 V Voff ≈ VI(BATT) Input VIT ≈ 2.5 V GND Figure 18. Single-Supply Comparator With Temperature-Compensated Threshold VI(BATT) R (see Note A) 2N222 2N222 30 Ω 0.01 µF VO 4.7 kΩ TL431 ǒ Ǔ + 1 ) R1 V R2 VO R2 0.1% R1 0.1% NOTE A: R should provide cathode current ≥1 mA to the TL431 at minimum VI(BATT). Figure 19. Precision High-Current Series Regulator 14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 ref TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 APPLICATION INFORMATION VI(BATT) IN uA7805 OUT Common VO R1 TL431 ǒ Ǔ + 1 ) R1 V R2 Minimum V + V ) 5 V VO ref ref O R2 Figure 20. Output Control of a Three-Terminal Fixed Regulator VI(BATT) VO R1 VO ǒ Ǔ + 1 ) R1 V R2 ref TL431 R2 Figure 21. High-Current Shunt Regulator VI(BATT) VO R1 TL431 R2 C (see Note A) NOTE A: Refer to the stability boundary conditions in Figure 16 to determine allowable values for C. Figure 22. Crowbar Circuit POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 15 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 APPLICATION INFORMATION IN VI(BATT) LM317 8.2 kΩ OUT Adjust VO ≈ 5 V, 1.5 A 243 Ω 0.1% TL431 243 Ω 0.1% Figure 23. Precision 5-V 1.5-A Regulator VO ≈ 5 V VI(BATT) Rb (see Note A) 27.4 kΩ 0.1% TL431 27.4 kΩ 0.1% NOTE A: Rb should provide cathode current ≥1-mA to the TL431. Figure 24. Efficient 5-V Precision Regulator 12 V VCC 6.8 kΩ 5V 10 kΩ – 10 kΩ 0.1% TL431 10 kΩ 0.1% + X Not Used TL598 Feedback Figure 25. PWM Converter With Reference 16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 APPLICATION INFORMATION R3 (see Note A) VI(BATT) R4 (see Note A) R1B R1A TL431 R2A ǒ Ǔ ǒ Ǔ V + 1 ) R1B R2B High Limit + 1 ) R1A V R2A Low Limit ref ref LED on When Low Limit < VI(BATT) < High Limit R2B NOTE A: R3 and R4 are selected to provide the desired LED intensity and cathode current ≥1 mA to the TL431 at the available VI(BATT). Figure 26. Voltage Monitor 650 Ω 12 V 2 kΩ R TL431 Off Delay +R C In ǒ Ǔ * 12 V 12 V V ref C On Figure 27. Delay Timer RCL 0.1% VI(BATT) R1 TL431 IO I out + RV ) I R1 + ref CL KA V I(BATT) I O h FE )I KA Figure 28. Precision Current Limiter POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 17 TL431, TL431A ADJUSTABLE PRECISION SHUNT REGULATORS SLVS005J – JULY 1978 – REVISED JULY 1999 APPLICATION INFORMATION VI(BATT) IO IO TL431 + VR ref S RS 0.1% Figure 29. Precision Constant-Current Sink 18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. 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