TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
D
Equivalent Full-Range Temperature
Coefficient . . . 30 ppm/°C
D
0.2-Ω Typical Output Impedance
D
Sink-Current Capability ...1 mA to 100 mA
D
Low Output Noise
D
Adjustable Output Voltage ...V
ref to 36 V
D
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.
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.
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.
1
2
3
4
8
7
6
5
CATHODE
ANODE
ANODE
NC
REF
ANODE
ANODE
NC
D PACKAGE
(TOP VIEW)
1
2
3
4
8
7
6
5
CATHODE
NC
NC
NC
REF
NC
ANODE
NC
P OR PW PACKAGE
(TOP VIEW)
PK PACKAGE
(TOP VIEW)
LP PACKAGE
(TOP VIEW)
REF ANODE CATHODE
CATHODE
ANODE
REF
CATHODE
ANODE
REF
ANODE
KTP PACKAGE
(TOP VIEW)
NC – No internal connection
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.
Copyright 1999, Texas Instruments Incorporated
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
2POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
AVAILABLE OPTIONS
PACKAGED DEVICES
TASMALL
OUTLINE
(D)
PLASTIC
FLANGE
MOUNT
(KTP)
TO-226AA
(LP)
PLASTIC
DIP
(P)
SOT-89
(PK)
SHRINK
SMALL
OUTLINE
(PW)
CHIP
FORM
(Y)
0°C to 70°CTL431CD
TL431ACD TL431CKTPR TL431CLP
TL431ACLP TL431CP
TL431ACP TL431CPK TL431CPW
TL431Y
–40°C to 85°CTL431ID
TL431AID TL431ILP
TL431AILP TL431IP
TL431AIP TL431IPK
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
CATHODEANODE
functional block diagram
CATHODE
REF
ANODE
+
_
Vref
equivalent schematic†
ANODE
REF
CATHODE
2.4 kΩ7.2 kΩ
3.28 kΩ
20 pF
4 kΩ
1 kΩ
800 Ω
800 Ω800 Ω
20 pF
150 Ω
10 kΩ
†All component values are nominal.
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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 af fect 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
MIN MAX UNIT
Cathode voltage, VKA Vref 36 V
Cathode current, IKA 1 100 mA
O
p
erating free air tem
p
erature range TA
TL431C, TL431AC 0 70 °
C
Operating
free
-
air
temperat
u
re
range
,
T
ATL431I, TL431AI –40 85
°C
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
4POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
PARAMETER
TEST
TEST CONDITIONS
TL431C
UNIT
PARAMETER
CIRCUIT
TEST
CONDITIONS
MIN TYP MAX
UNIT
Vref Reference voltage 2 VKA = V ref, IKA = 10 mA 2440 2495 2550 mV
VI(dev) Deviation of reference voltage
over full temperature range
(see Figure 1) 2VKA = V ref, IKA = 10 mA,
TA = full range†4 25 mV
D
V
ref
Ratio of change in reference voltage
3
IKA =10mA
∆VKA = 10 V – Vref –1.4 –2.7
mV
ref
D
VKA
gg
to the change in cathode voltage
3
I
KA =
10
mA
∆VKA = 36 V – 10 V –1 –2
mV
V
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) 3IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range†0.4 1.2 µA
Imin Minimum cathode current
for regulation 2 VKA = V ref 0.4 1 mA
Ioff Of f-state cathode current 4 VKA = 36 V, Vref = 0 0.1 1µA
|zKA|Dynamic impedance (see Figure 1) 1IKA = 1 mA to 100 mA, VKA = Vref,
f ≤ 1 kHz 0.2 0.5 Ω
†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:
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
Because minimum Vref occurs at the lower temperature, the coefficient is positive.
Calculating Dynamic Impedance
The dynamic impedance is defined as:
When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit
is given by:
Maximum Vref
Minimum Vref
∆TA
VI(dev)
Ť
a
Vref
Ťǒ
ppm
°C
Ǔ+ǒ
VI(dev)
Vref at 25°C
Ǔ
106
D
TA
Ť
a
Vref
Ť+ǒ
4mV
2495 mV
Ǔ
106
70°C
[
23 ppm
ń
°C
Ť
zKA
Ť+
D
VKA
D
IKA
|z
Ȁ
|
+
D
V
D
I
[Ť
zKA
Ťǒ
1
)
R1
R2
Ǔ
Figure 1. Calculating Deviation Parameters and Dynamic Impedance
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
PARAMETER
TEST
TEST CONDITIONS
TL431I
UNIT
PARAMETER
CIRCUIT
TEST
CONDITIONS
MIN TYP MAX
UNIT
Vref Reference voltage 2 VKA = V ref, IKA = 10 mA 2440 2495 2550 mV
VI(dev) Deviation of reference voltage
over full temperature range
(see Figure 1) 2VKA = V ref, IKA = 10 mA,
TA = full range†5 50 mV
D
V
ref
Ratio of change in reference voltage
3
IKA =10mA
∆VKA = 10 V – V ref –1.4 –2.7
mV
ref
D
VKA
gg
to the change in cathode voltage
3
I
KA =
10
mA
∆VKA = 36 V – 10 V –1 –2
mV
V
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) 3IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range†0.8 2.5 µA
Imin Minimum cathode current for
regulation 2 VKA = V ref 0.4 1 mA
Ioff Of f-state cathode current 4 VKA = 36 V, Vref = 0 0.1 1µA
|zKA|Dynamic impedance (see Figure 1) 2IKA = 1 mA to 100 mA, VKA = Vref,
f ≤ 1 kHz 0.2 0.5 Ω
†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
TEST CONDITIONS
TL431AC
UNIT
PARAMETER
CIRCUIT
TEST
CONDITIONS
MIN TYP MAX
UNIT
Vref Reference voltage 2 VKA = V ref, IKA = 10 mA 2470 2495 2520 mV
VI(dev) Deviation of reference voltage
over full temperature range
(see Figure 1) 2VKA = V ref, IKA = 10 mA,
TA = full range†4 25 mV
D
V
ref
Ratio of change in reference voltage
3
IKA =10mA
∆VKA = 10 V – V ref –1.4 –2.7
mV
ref
D
VKA
gg
to the change in cathode voltage
3
I
KA =
10
mA
∆VKA = 36 V – 10 V –1 –2
mV
V
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) 3IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range‡0.8 1.2 µA
Imin Minimum cathode current
for regulation 2 VKA = V ref 0.4 0.6 mA
Ioff Of f-state cathode current 4 VKA = 36 V, Vref = 0 0.1 0.5 µA
|zKA|Dynamic impedance (see Figure 1) 1IKA = 1 mA to 100 mA, VKA = Vref,
f ≤ 1 kHz 0.2 0.5 Ω
‡Full range is 0°C to 70°C for the TL431AC.
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
6POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
PARAMETER
TEST
TEST CONDITIONS
TL431AI
UNIT
PARAMETER
CIRCUIT
TEST
CONDITIONS
MIN TYP MAX
UNIT
Vref Reference voltage 2 VKA = V ref, IKA = 10 mA 2470 2495 2520 mV
VI(dev) Deviation of reference voltage
over full temperature range
(see Figure 1) 2VKA = V ref, IKA = 10 mA,
TA = full range†5 50 mV
D
V
ref
Ratio of change in reference voltage
3
IKA =10mA
∆VKA = 10 V – Vref –1.4 –2.7
mV
ref
D
VKA
gg
to the change in cathode voltage
3
I
KA =
10
mA
∆VKA = 36 V – 10 V –1 –2
mV
V
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) 3IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range†0.8 2.5 µA
Imin Minimum cathode current
for regulation 2 VKA = V ref 0.4 0.7 mA
Ioff Of f-state cathode current 4 VKA = 36 V, Vref = 0 0.1 0.5 µA
|zKA|Dynamic impedance (see Figure 1) 2IKA = 1 mA to 100 mA, VKA = Vref,
f ≤ 1 kHz 0.2 0.5 Ω
†Full range is –40°C to 85°C for the TL431AI.
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
PARAMETER
TEST
TEST CONDITIONS
TL431Y
UNIT
PARAMETER
CIRCUIT
TEST
CONDITIONS
MIN TYP MAX
UNIT
Vref Reference voltage 2 VKA = V ref, IKA = 10 mA 2495 mV
D
V
ref
Ratio of change in reference voltage
3
IKA =10mA
∆VKA = 10 V – Vref –1.4
mV
ref
D
VKA
gg
to the change in cathode voltage
3
I
KA =
10
mA
∆VKA = 36 V – 10 V –1
mV
V
Iref Reference input current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞2µA
Imin Minimum cathode current
for regulation 2 VKA = V ref 0.4 mA
Ioff Of f-state cathode current 4 VKA = 36 V, Vref = 0 0.1 µA
|zKA|Dynamic impedance‡2IKA = 1 mA to 100 mA, VKA = Vref,
f ≤ 1 kHz 0.2 Ω
‡Calculating dynamic impedance:
The dynamic impedance is defined as:
Ť
zKA
Ť+
D
VKA
D
IKA
When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit is given by:
|z
Ȁ
|
+
∆V
∆I
[
|zKA|
ǒ
1
)
R1
R2
Ǔ
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER MEASUREMENT INFORMATION
Vref
Input VKA
IKA
Figure 2. Test Circuit for VKA = Vref
VKA
+
Vref
ǒ
1
)
R1
R2
Ǔ)
Iref
R1
Iref
IKA
VKA
Input
Vref
R1
R2
Figure 3. Test Circuit for VKA > Vref
Ioff
VKA
Input
Figure 4. Test Circuit for Ioff
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
8POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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 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
V oltage monitor 26
Delay timer 27
Precision current limiter 28
Precision constant-current sink 29
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS†
‡Data is for devices having the indicated value of V ref at IKA = 10 mA,
TA = 25°C.
Figure 5
2500
2480
2420
2400
–75 –50 –25 0 25 50 75
2540
2580
REFERENCE VOLTAGE
vs
FREE-AIR TEMPERATURE
2600
100 125
2460
2560
2520
2440
TA – Free-Air Temperature – °C
Vref = 2495 mV‡
Vref = 2440 mV‡
VKA = Vref
IKA = 10 mA Vref = 2550 mV‡
– Reference Voltage – mV
Vref
Figure 6
3
2
1
0
–75 –25 0 50
4
REFERENCE CURRENT
vs
FREE-AIR TEMPERATURE
5
100 125
–50 25 75
TA – Free-Air Temperature – °C
R1 = 10 kΩ
R2 = ∞
IKA = 10 mA
– Reference Current –ref
IAµ
Figure 7
25
0
–50
–75
–100
125
–25
–2 –1 0 1
75
50
100
CATHODE CURRENT
vs
CATHODE VOLTAGE
150
23
VKA – Cathode Voltage – V
VKA = Vref
TA = 25°C
– Cathode Current – mAIKA
Figure 8
400
200
0
–200–1 0 1
600
CATHODE CURRENT
vs
CATHODE VOLTAGE
800
23
VKA = Vref
TA = 25°C
VKA – Cathode Voltage – V
Imin
– Cathode Current –
IKA Aµ
†Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the various devices.
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS†
Figure 9
1.5
1
0.5
0
–75 –25 0 50
– Off-State Cathode Current –
2
OFF-STATE CATHODE CURRENT
vs
FREE-AIR TEMPERATURE
2.5
100 125
–50 25 75
Ioff Aµ
TA – Free-Air Temperature – °C
VKA = 36 V
Vref = 0
Figure 10
–1.15
–1.25
–1.35
–1.45
–1.05
– 0.95
RATIO OF DELTA REFERENCE VOLTAGE TO
DELTA CATHODE VOLTAGE
vs
FREE-AIR TEMPERATURE
– 0.85
TA – Free-Air Temperature – °C
–75 –25 0 50 100 125–50 25 75
VKA = 3 V to 36 V
– mV/V
∆Vref ∆VKA
/
180
140
120
10010 100 1 k
220
240
f – Frequency – Hz
EQUIVALENT INPUT NOISE VOLTAGE
vs
FREQUENCY
260
10 k 100 k
200
160
– Equivalent Input Noise Voltage – nV/ HzVn
IO = 10 mA
TA = 25°C
Figure 11
†Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the various devices.
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
11
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
19.1 V
VCC
TLE2027
TLE2027
AV = 10 V/mV
VEE
0.1 µF
160 kΩ
820 Ω
(DUT)
TL431
16 Ω
910 Ω2000 µF
1 kΩ
VEE
VCC
1 µF
16 kΩ16 kΩ
1 µF33 kΩ
33 kΩAV = 2 V/V
22 µF
500 µF
To Oscilloscope
–1
–2
–4
–5
–6
3
–3
0123456
1
0
2
EQUIVALENT INPUT NOISE VOLTAGE
OVER A 10-SECOND PERIOD
4
78910
5
6
t – Time – s
f = 0.1 to 10 Hz
IKA = 10 mA
TA = 25°C
– Equivalent Input Noise voltage – µV
Vn
+
–+
–
Figure 12. Test Circuit for Equivalent Input Noise Voltage
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
SMALL-SIGNAL VOLTAGE AMPLIFICATION
vs
FREQUENCY
9 µF
GND
Output
232 Ω
8.25 kΩ
IKA
15 kΩ
40
20
10
0
60
30
1 k 10 k 100 k 1 M 10 M
50
f – Frequency – Hz
TEST CIRCUIT FOR VOLTAGE AMPLIFICATION
IKA = 10 mA
TA = 25°C
– Small-Signal Voltage Amplification – dBAV
+
–
Figure 13
1 kΩ
50 Ω
GND
Output
IKA
0.1
1 k 10 k 100 k 1 M 10 M
1
f – Frequency – Hz
REFERENCE IMPEDANCE
vs
FREQUENCY
10
100 IKA = 10 mA
TA = 25°C
TEST CIRCUIT FOR REFERENCE IMPEDANCE
– Reference Impedance –
KA
|z | Ω
+
–
Figure 14
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
3
2
1
0–1 0 1 2 3 4
Input and Output Voltage – V
4
5
PULSE RESPONSE
6
567
Input
Output
TA = 25°C
220 Ω
50 Ω
GND
Output
Pulse
Generator
f = 100 kHz
TEST CIRCUIT FOR PULSE RESPONSE
t – Time – µs
Figure 15
50
40
10
0
0.001 0.01 0.1 1
70
90
STABILITY BOUNDARY CONDITIONS†
100
10
30
80
60
20
TA = 25°C
B
Stable
Stable
A VKA = Vref
B VKA = 5 V
C VKA = 10 V
D VKA = 15 Vf
CL – Load Capacitance – µF
A
C
D
150 Ω
IKA
R1 = 10 kΩ
R2
CL
VBATT
IKA
CLVBATT
150 Ω
TEST CIRCUIT FOR CURVE A
TEST CIRCUIT FOR CURVES B, C, AND D
– Cathode Current – mA
IKA
†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.
+
–
+
–
Figure 16
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
R1
0.1%
R2
0.1%
R
(see Note A)
Vref
VO
TL431
VI(BATT)
RETURN
NOTE A: R should provide cathode current ≥1 mA to the TL431 at minimum VI(BATT).
VO
+ǒ
1
)
R1
R2
Ǔ
Vref
Figure 17. Shunt Regulator
VO
TL431
VI(BATT)
VIT ≈2.5 V GND
Input Von ≈ 2 V
Voff ≈ VI(BATT)
Figure 18. Single-Supply Comparator With Temperature-Compensated Threshold
R
(see Note A)
VO
TL431
VI(BATT)
2N222
2N222
4.7 kΩ
R1
0.1%
R2
0.1%
0.01 µF
30 Ω
VO
+ǒ
1
)
R1
R2
Ǔ
Vref
NOTE A: R should provide cathode current ≥1 mA to the TL431 at minimum VI(BATT).
Figure 19. Precision High-Current Series Regulator
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
VO
TL431
VI(BATT)
uA7805
IN OUT
Common R1
R2
VO
+ǒ
1
)
R1
R2
Ǔ
Vref
Minimum VO
+
Vref
)
5V
Figure 20. Output Control of a Three-Terminal Fixed Regulator
VO
TL431
VI(BATT)
R1
R2
VO
+ǒ
1
)
R1
R2
Ǔ
Vref
Figure 21. High-Current Shunt Regulator
VO
TL431
VI(BATT)
R1
R2
NOTE A: Refer to the stability boundary conditions in Figure 16 to determine allowable values for C.
C
(see Note A)
Figure 22. Crowbar Circuit
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
VO ≈ 5 V, 1.5 A
TL431
VI(BATT) LM317
IN OUT
Adjust 243 Ω
0.1%
243 Ω
0.1%
8.2 kΩ
Figure 23. Precision 5-V 1.5-A Regulator
VO ≈ 5 V
TL431
VI(BATT)
27.4 kΩ
0.1%
Rb
(see Note A)
27.4 kΩ
0.1%
NOTE A: Rb should provide cathode current ≥1-mA to the TL431.
Figure 24. Efficient 5-V Precision Regulator
TL431
12 V
VCC
5 V
6.8 kΩ
10 kΩ
10 kΩ
0.1%
10 kΩ
0.1%
X
Not
Used
Feedback
TL598
+
–
Figure 25. PWM Converter With Reference
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
17
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
TL431
VI(BATT)
R3
(see Note A)
R1A R4
(see Note A)
R2BR2A
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).
R1B Low Limit
+ǒ
1
)
R1B
R2B
Ǔ
Vref
High Limit
+ǒ
1
)
R1A
R2A
Ǔ
Vref
LED on When Low Limit < VI(BATT) < High Limit
Figure 26. Voltage Monitor
TL431
650 Ω
2 kΩ
C
On
Off
R
12 V
Delay
+
R
C
In
ǒ
12 V
12 V
*
Vref
Ǔ
Figure 27. Delay Timer
TL431
IO
RCL
0.1%
R1
VI(BATT) Iout
+
Vref
RCL
)
IKA
R1
+
VI(BATT)
IO
hFE
)
IKA
Figure 28. Precision Current Limiter
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
TL431 RS
0.1%
IO
VI(BATT)
IO
+
Vref
RS
Figure 29. Precision Constant-Current Sink
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