TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y

ADJUSTABLE PRECISION SHUNT REGULATORS

SLVS005I – JULY 1978 – REVISED AUGUST 1998

D Equivalent Full-Range Temperature D PACKAGE

Coefficient . . . 30 ppm/°C (TOP VIEW)

D 0.2-Ω Typical Output Impedance CATHODE 1 8 REF

D Sink-Current Capability . . . 1 mA to 100 mA ANODE 2 7 ANODE
D Low Output Noise ANODE 3 6 ANODE
D Adjustable Output Voltage . . . Vref to 36 V NC 4 5 NC

D Available in a Wide Range of High-Density

Packages JG, P, OR PW PACKAGE
(TOP VIEW)
description
CATHODE 1 8 REF
The TL431 and TL431A are 3-terminal adjustable NC 2 7 NC
shunt regulators with specified thermal stability NC 3 6 ANODE
over applicable automotive, commercial, and NC 4 5 NC
military temperature ranges. The output voltage
can be set to any value between Vref
PK PACKAGE
(approximately 2.5 V) and 36 V with two external (TOP VIEW)
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 on-board regulation,
adjustable power supplies, and switching power REF ANODE CATHODE
supplies.
LP PACKAGE
The TL431C and TL431AC are characterized for (TOP VIEW)
operation from 0°C to 70°C, and the TL431I and
TL431AI are characterized for operation from CATHODE
–40°C to 85°C. The TL431M is characterized for ANODE
operation over the full military temperature range
of –55°C to 125°C. REF

FK PACKAGE KTP PACKAGE

(TOP VIEW) (TOP VIEW)
CATHODE

CATHODE
ANODE ANODE
REF
NC

NC

NC

REF
3 2 1 20 19
NC 4 18 NC
NC 5 17 NC
NC 6 16 NC
NC 7 15 ANODE
NC 8 14 NC
9 10 11 12 13
NC
NC
NC
NC
NC

NC – No internal connection

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.

PRODUCTION DATA information is current as of publication date. Copyright  1998, Texas Instruments Incorporated
Products conform to specifications per the terms of Texas Instruments On products compliant to MIL-PRF-38535, all parameters are tested
standard warranty. Production processing does not necessarily include unless otherwise noted. On all other products, production
testing of all parameters. processing does not necessarily include testing of all parameters.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 1

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

AVAILABLE OPTIONS
PACKAGED DEVICES
PLASTIC SHRINK CHIP
TA SMALL CHIP CERAMIC PLASTIC FORM
FLANGE TO-226AA SOT-89 SMALL
OUTLINE CARRIER DIP DIP (Y)
MOUNT (LP) (PK) OUTLINE
(D) (FK) (JG) (P)
(KTP) (PW)
0°C
TL431CD TL431CLP TL431CP
to TL431CKTPR TL431CPK TL431CPW
TL431ACD TL431ACLP TL431ACP
70°C
–40°C
TL431ID TL431ILP TL431IP
to TL431IPK TL431Y
TL431AID TL431AILP TL431AIP
85°C
–55°C
to TL431MFK TL431MJG
125°C
The D and LP packages are available taped and reeled. Add R suffix to device type (e.g., TL431CDR). The KTP and PK packages are only available
taped and reeled. Chip forms are tested at TA = 25°C.

symbol
REF

ANODE CATHODE

functional block diagram

CATHODE

REF +
_

Vref

ANODE

2 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

equivalent schematic†
CATHODE
800 Ω 800 Ω

20 pF
REF

150 Ω

3.28 kΩ
4 kΩ 10 kΩ

2.4 kΩ 7.2 kΩ 20 pF

1 kΩ

800 Ω

ANODE
† All component values are nominal.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 3

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

TL431Y chip information

This chip, when properly assembled, displays characteristics similar to those of the TL431C. Thermal
compression or ultrasonic bonding can be used on the doped-aluminum bonding pads. The chip can be
mounted with conductive epoxy or a gold-silicon preform.

Bonding Pad Assignments

(1)

(1)
CATHODE
(3)
(2) TL431Y REF
ANODE
41

Chip Thickness: 15 Mils Typical

Bonding Pads: 4 × 4 Mils Minimum
(3) TJ(max) = 150°C
(2) Tolerances Are ±10%.
All Dimensions Are in Mils.
Pins 2, 3, 6, and 7 Are Connected Together.
Pins 4 and 5 Are Not Connected.

51

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
Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Tables 1 and 2
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
Case temperature for 60 seconds: FK package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
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: JG, LP, or PK package . . . . . . . . . . 300°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.
NOTE 1: Voltage values are with respect to the anode terminal unless otherwise noted.

4 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

DISSIPATION RATING TABLE 1 – FREE-AIR TEMPERATURE

TA = 25°C DERATING FACTOR TA = 70°C TA = 85°C TA = 125°C
PACKAGE
POWER RATING ABOVE TA = 25°C POWER RATING POWER RATING POWER RATING
D 725 mW 5.8 mW/°C 464 mW 377 mW —
FK 1375 mW 11 mW/°C 880 mW 715 mW 275 mW
JG 1050 mW 8.4 mW/°C 672 mW 546 mW 210 mW
KTP 1800 mW 14.5 mW/°C 1147 mW 943 mW —
LP 775 mW 6.2 mW/°C 496 mW 403 mW —
P 1000 mW 8 mW/°C 640 mW 520 mW —
PK 500 mW 4 mW/°C 320 mW 260 mW —
PW 525 mW 4.2 mW/°C 336 mW — —

DISSIPATION RATING TABLE 2 – CASE TEMPERATURE

TC = 25°C DERATING FACTOR TC = 70°C TC = 85°C
PACKAGE
POWER RATING ABOVE TC = 25°C POWER RATING POWER RATING
PK 3125 mW 25 mW/°C 2000 mW 1625 mW

recommended operating conditions

MIN MAX UNIT
Cathode voltage, VKA Vref 36 V
Cathode current, IKA 1 100 mA
C suffix 0 70
Operating free-air temperature range, TA I suffix –40 85 °C
M suffix –55 125

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 5

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise

noted)
TEST TL431C
PARAMETER TEST CONDITIONS UNIT
CIRCUIT MIN TYP MAX
Vref Reference voltage 2 VKA = Vref, IKA = 10 mA 2440 2495 2550 mV
Deviation of reference voltage
VKA = Vref, IKA = 10 mA,
VI(dev) over full temperature range 2 4 25 mV
TA = Full range†
(see Figure 1)
DVref Ratio of change in reference voltage
3 IKA = 10 mA
∆VKA = 10 V – Vref –1.4 –2.7 mV
DVKA to the change in cathode voltage ∆VKA = 36 V – 10 V –1 –2 V
Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
II(dev) over full temperature range 3 0.4 1.2 µA
TA = Full range†
(see Figure 1)
Minimum cathode current
Imin 2 VKA = Vref 0.4 1 mA
for regulation
Ioff Off-state cathode current 4 VKA = 36 V, Vref = 0 0.1 1 µA
IKA = 1 mA to 100 mA, VKA = Vref,
|zKA| Dynamic impedance (see Figure 1) 1 0.2 0.5 Ω
f ≤ 1 kHz
† Full temperature 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 Ǔ+
ppm
ǒ Ǔ V
I(dev)
V at 25°C
ref
10 6
Maximum Vref
VI(dev)

Vref
°C DTA 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

Ťa Ť + ǒ Ǔ [ 23 ppmń°C
4 mV
2495 mV
10 6
Vref
70°C
Because minimum Vref occurs at the lower temperature, the coefficient is positive.
Calculating Dynamic Impedance
The dynamic impedance is defined as: |z KA| + DDVI KA
KA

When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit
is given by:
|z | Ȁ+ [
DV |zKA| 1 R1
DI R2
ǒ) Ǔ
Figure 1. Calculating Deviation Parameters and Dynamic Impedance

6 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise

noted)
TEST TL431I
PARAMETER TEST CONDITIONS UNIT
CIRCUIT MIN TYP MAX
Vref Reference voltage 2 VKA = Vref, IKA = 10 mA 2440 2495 2550 mV
Deviation of reference voltage
VKA = Vref, IKA = 10 mA,
VI(dev) over full temperature range 2 5 50 mV
TA = Full range†
(see Figure 1)
DVref Ratio of change in reference voltage
3 IKA = 10 mA
∆VKA = 10 V – Vref –1.4 –2.7 mV
DVKA to the change in cathode voltage ∆VKA = 36 V – 10 V –1 –2 V
Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
II(dev) over full temperature range 3 0.8 2.5 µA
TA = Full range†
(see Figure 1)
Minimum cathode current for
Imin 2 VKA = Vref 0.4 1 mA
regulation
Ioff Off-state cathode current 4 VKA = 36 V, Vref = 0 0.1 1 µA
IKA = 1 mA to 100 mA, VKA = Vref,
|zKA| Dynamic impedance (see Figure 1) 2 0.2 0.5 Ω
f ≤ 1 kHz
† Full temperature range is –40°C to 85°C for the TL431I.

electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise

noted)
TEST TL431M
PARAMETER TEST CONDITIONS UNIT
CIRCUIT MIN TYP MAX
Vref Reference voltage 2 VKA = Vref, IKA = 10 mA 2400 2495 2600 mV
Deviation of reference voltage
VKA = Vref, IKA = 10 mA,
VI(dev) over full temperature range 2 22 mV
TA = Full range†
(see Figure 1)
DVref Ratio of change in reference voltage
3 IKA = 10 mA
∆VKA = 10 V – Vref –1.4 –3 mV
DVKA to the change in cathode voltage ∆VKA = 36 V – 10 V –1 –2.3 V
Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 8* µA
Deviation of reference current
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
II(dev) over full temperature range 3 1 µA
TA = Full range‡
(see Figure 1)
Minimum cathode current
Imin 2 VKA = Vref 0.4 1.5 mA
for regulation
Ioff Off-state cathode current 4 VKA = 36 V, Vref = 0 0.1 3 µA
IKA = 1 mA to 100 mA, VKA = Vref,
|zKA| Dynamic impedance (see Figure 1) 1 0.2 0.9* Ω
f ≤ 1 kHz
* On products compliant to MIL-PRF-38535, this parameter is not production tested.
‡ Full temperature range is –55°C to 125°C for the TL431M.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 7

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise

noted)
TEST TL431AC
PARAMETER TEST CONDITIONS UNIT
CIRCUIT MIN TYP MAX
Vref Reference voltage 2 VKA = Vref, IKA = 10 mA 2470 2495 2520 mV
Deviation of reference voltage
VKA = Vref, IKA = 10 mA,
VI(dev) over full temperature range 2 4 25 mV
TA = Full range†
(see Figure 1)
DVref Ratio of change in reference voltage
3 IKA = 10 mA
∆VKA = 10 V – Vref –1.4 –2.7 mV
DVKA to the change in cathode voltage ∆VKA = 36 V – 10 V –1 –2 V
Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
II(dev) over full temperature range 3 0.8 1.2 µA
TA = Full range†
(see Figure 1)
Minimum cathode current
Imin 2 VKA = Vref 0.4 0.6 mA
for regulation
Ioff Off-state cathode current 4 VKA = 36 V, Vref = 0 0.1 0.5 µA
IKA = 1 mA to 100 mA, VKA = Vref,
|zKA| Dynamic impedance (see Figure 1) 1 0.2 0.5 Ω
f ≤ 1 kHz
† Full temperature range is 0°C to 70°C for the TL431AC.

electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise

noted)
TEST TL431AI
PARAMETER TEST CONDITIONS UNIT
CIRCUIT MIN TYP MAX
Vref Reference voltage 2 VKA = Vref, IKA = 10 mA 2470 2495 2520 mV
Deviation of reference voltage
VKA = Vref, IKA = 10 mA,
VI(dev) over full temperature range 2 5 50 mV
TA = Full range†
(see Figure 1)
DVref Ratio of change in reference voltage
3 IKA = 10 mA
∆VKA = 10 V – Vref –1.4 –2.7 mV
DVKA to the change in cathode voltage ∆VKA = 36 V – 10 V –1 –2 V
Iref Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
II(dev) over full temperature range 3 0.8 2.5 µA
TA = Full range‡
(see Figure 1)
Minimum cathode current
Imin 2 VKA = Vref 0.4 0.7 mA
for regulation
Ioff Off-state cathode current 4 VKA = 36 V, Vref = 0 0.1 0.5 µA
IKA = 1 mA to 100 mA, VKA = Vref,
|zKA| Dynamic impedance (see Figure 1) 2 0.2 0.5 Ω
f ≤ 1 kHz
‡ Full temperature range is –40°C to 85°C for the TL431AI.

8 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise

noted)
TEST TL431Y
PARAMETER TEST CONDITIONS UNIT
CIRCUIT MIN TYP MAX
Vref Reference voltage 2 VKA = Vref, IKA = 10 mA 2495 mV
DVref Ratio of change in reference voltage
3 IKA = 10 mA
∆VKA = 10 V – Vref –1.4 mV
DVKA to the change in cathode voltage ∆VKA = 36 V – 10 V –1 V
Iref Reference input current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 µA
Minimum cathode current
Imin 2 VKA = Vref 0.4 mA
for regulation
Ioff Off-state cathode current 4 VKA = 36 V, Vref = 0 0.1 µA
IKA = 1 mA to 100 mA, VKA = Vref,
|zKA| Dynamic impedance† 2 0.2 Ω
f ≤ 1 kHz
† Calculating dynamic impedance:

The dynamic impedance is defined as: z Ť Ť + DD

KA
V KA
I KA

Ȁ + ∆V
|z |
∆I
[ |z KA
ǒ) Ǔ
When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit is given by:

| 1 R1
R2

PARAMETER MEASUREMENT INFORMATION

Input VKA Input VKA

IKA IKA

R1 Iref

Vref R2 Vref
V KA +V ǒ ) Ǔ)
ref 1 R1
R2
I ref R1

Figure 2. Test Circuit for VKA = Vref Figure 3. Test Circuit for VKA > Vref

Input VKA
Ioff

Figure 4. Test Circuit for Ioff

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 9

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

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
Shunt regulator 17
Single-supply comparator with temperature-compensated threshold 18
Precision high-current series regulator 19
Output control of a 3-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

10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

TYPICAL CHARACTERISTICS

REFERENCE VOLTAGE REFERENCE CURRENT

vs vs
FREE-AIR TEMPERATURE† FREE-AIR TEMPERATURE†
2600
VKA = Vref 5
R1 = 10 kΩ
2580 IKA = 10 mA R2 = ∞
Vref = 2550 mV‡ IKA = 10 mA
V ref – Reference Voltage – mV

2560
4

I ref – Reference Current – µ A

2540

2520 3
Vref = 2495 mV‡
2500

2480
2

2460

2440 Vref = 2440 mV‡

1

2420

2400 0
–75 –50 –25 0 25 50 75 100 125
–75 –50 –25 0 25 50 75 100 125
TA – Free-Air Temperature – °C TA – Free-Air Temperature – °C
† Data is applicable only within the recommended operating free-air † Data is applicable only within the recommended operating free-air
temperature ranges of the various devices. temperature ranges of the various devices.
‡ Data is for devices having the indicated value of Vref at IKA = 10 mA,
TA = 25°C.
Figure 5 Figure 6

CATHODE CURRENT CATHODE CURRENT

vs vs
CATHODE VOLTAGE CATHODE VOLTAGE
150 800
VKA = Vref VKA = Vref
125 TA = 25°C TA = 25°C

100 600
I KA – Cathode Current – mA

I KA – Cathode Current – µ A

75 Imin

50 400

25

0 200

–25

–50 0

–75

–100 –200
–2 –1 0 1 2 3 –1 0 1 2 3
VKA – Cathode Voltage – V VKA – Cathode Voltage – V
Figure 7 Figure 8

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 11

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

TYPICAL CHARACTERISTICS

RATIO OF DELTA REFERENCE VOLTAGE TO

OFF-STATE CATHODE CURRENT DELTA CATHODE VOLTAGE
vs vs
FREE-AIR TEMPERATURE† FREE-AIR TEMPERATURE†
2.5 – 0.85
VKA = 36 V
VKA = 3 V to 36 V
Vref = 0
I off – Off-State Cathode Current – µ A

– 0.95
2

∆V ref / ∆V KA – mV/V
–1.05
1.5

–1.15

1
–1.25

0.5
–1.35

0 –1.45
–75 –50 –25 0 25 50 75 100 125 –75 –50 –25 0 25 50 75 100 125
TA – Free-Air Temperature – °C TA – Free-Air Temperature – °C
† Data is applicable only within the recommended operating free-air † Data is applicable only within the recommended operating free-air
temperature ranges of the various devices. temperature ranges of the various devices.

Figure 9 Figure 10

EQUIVALENT INPUT NOISE VOLTAGE

vs
FREQUENCY
260
Vn – Equivalent Input Noise Voltage – nV/ Hz

IO = 10 mA
240 TA = 25°C

220

200

180

160

140

120

100
10 100 1k 10 k 100 k
f – Frequency – Hz

Figure 11

12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

TYPICAL CHARACTERISTICS
EQUIVALENT INPUT NOISE VOLTAGE
OVER A 10-SECOND PERIOD
6
5

V n – Equivalent Input Noise voltage – µV

4
3
2

0
–1

–2
–3

–4 f = 0.1 to 10 Hz
IKA = 10 mA
–5
TA = 25°C
–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 VCC To Oscilloscope
1 µF
TL431
(DUT) TLE2027
AV = 10 V/mV
+ 22 µF
TLE2027
820 Ω +
– 16 kΩ 16 kΩ
16 Ω –
160 kΩ
1 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 13

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

TYPICAL CHARACTERISTICS
SMALL-SIGNAL VOLTAGE AMPLIFICATION
vs
FREQUENCY
60
IKA = 10 mA
A V – Small-Signal Voltage Amplification – dB

TA = 25°C
50 Output
IKA
15 kΩ 232 Ω
40
9 µF
+
30
–
8.25 kΩ

20 GND

10 TEST CIRCUIT FOR VOLTAGE AMPLIFICATION

0
1k 10 k 100 k 1M 10 M
f – Frequency – Hz

Figure 13

REFERENCE IMPEDANCE
vs
FREQUENCY
100
IKA = 10 mA
TA = 25°C
|z KA | – Reference Impedance – Ω

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

14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

TYPICAL CHARACTERISTICS
PULSE RESPONSE
6
TA = 25°C
Input
5
220 Ω
Input and Output Voltage – V

Output
4
Pulse
Generator 50 Ω
3 f = 100 kHz
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†

150 Ω
100
A VKA = Vref TA = 25°C
90 B VKA = 5 V IKA
C VKA = 10 V
+
80 D VKA = 15 Vf
CL VBATT
I KA – Cathode Current – mA

B –
70
Stable
60
Stable C
50
A TEST CIRCUIT FOR CURVE A
40

30
D IKA
20 R1 = 10 kΩ 150 Ω
10
CL
0 +
0.001 0.01 0.1 1 10 R2 VBATT
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. TEST CIRCUIT FOR CURVES B, C, AND D

Figure 16

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 15

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

APPLICATION INFORMATION
R
(see Note A)
VI(BATT) VO
R1

ǒ Ǔ
0.1%
Vref TL431 VO + 1 ) R1
R2
V ref

R2
0.1%

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
Input Voff ≈ VI(BATT)
VIT ≈ 2.5 V
GND

Figure 18. Single-Supply Comparator With Temperature-Compensated Threshold

VI(BATT)
R
(see Note A) 2N222

2N222

ǒ Ǔ
30 Ω

VO + 1 ) R1
R2
V ref
0.01 µF 4.7 kΩ
TL431 VO
R1
R2
0.1%
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

16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

APPLICATION INFORMATION
VI(BATT)
IN
OUT

ǒ Ǔ
uA7805 VO

Common R1 VO + 1 ) R1
R2
V ref

TL431 Minimum V + V ) 5 V
O ref

R2

Figure 20. Output Control of a 3-Terminal Fixed Regulator

VI(BATT) VO

R1

VO ǒ Ǔ
+ 1 ) R1
R2
V ref

R2 TL431

Figure 21. High-Current Shunt Regulator

VI(BATT) VO

R1

TL431

C
(see Note A)
R2

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 17

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

APPLICATION INFORMATION
IN OUT
VI(BATT) LM317 VO ≈ 5 V, 1.5 A

8.2 kΩ Adjust
243 Ω
0.1%

TL431
243 Ω
0.1%

Figure 23. Precision 5-V 1.5-A Regulator

VI(BATT) VO ≈ 5 V
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% TL598
X
TL431 Not
10 kΩ Used
0.1%

Feedback

Figure 25. PWM Converter With Reference

18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

 TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

APPLICATION INFORMATION
R3
(see Note A)
VI(BATT)

R1A R1B
R4
+ 1 ) R1B ǒ Ǔ
ǒ Ǔ
(see Note A)
Low Limit V ref
R2B
High Limit + 1 ) R1A V
TL431
R2A ref

LED on When Low Limit < VI(BATT) < High Limit

R2A 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

R 2 kΩ

TL431
Delay +R C In ǒ 12 V
12 V V ref * Ǔ
On C
Off

Figure 27. Delay Timer

RCL IO

+ RV ) I
0.1%
VI(BATT) ref
I out KA
CL

R1
R1 + V I(BATT)
TL431 O
h FE
I
)I KA

Figure 28. Precision Current Limiter

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265 19

TL431C, TL431AC, TL431I, TL431AI, TL431M, TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005I – JULY 1978 – REVISED AUGUST 1998

APPLICATION INFORMATION
VI(BATT)
IO

IO + VR
ref
S
TL431
RS
0.1%

Figure 29. Precision Constant-Current Sink

20 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

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