TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
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
D
Available in a Wide Range of High-Density
ref
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 V
(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.
to 36 V
ref
D PACKAGE
(TOP VIEW)
CATHODE
ANODE
ANODE
CATHODE
NC – No internal connection
1
2
3
4
NC
P OR PW PACKAGE
(TOP VIEW)
1
NC
2
NC
3
4
NC
PK PACKAGE
(TOP VIEW)
REF ANODE CATHODE
LP PACKAGE
(TOP VIEW)
8
7
6
5
8
7
6
5
REF
ANODE
ANODE
NC
REF
NC
ANODE
NC
CATHODE
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.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
ANODE
ANODE
REF
KTP PACKAGE
(TOP VIEW)
CATHODE
ANODE
REF
Copyright 1999, Texas Instruments Incorporated
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
1
TL431, TL431A
TL431Y
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
AVAILABLE OPTIONS
PACKAGED DEVICES
T
A
0°C to 70°C
–40°C to 85°C
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.
SMALL
OUTLINE
(D)
TL431CD
TL431ACD
TL431ID
TL431AID
symbol
functional block diagram
PLASTIC
FLANGE
MOUNT
(KTP)
TL431CKTPR
TO-226AA
(LP)
TL431CLP
TL431ACLP
TL431ILP
TL431AILP
REF
PLASTIC
DIP
(P)
TL431CP
TL431ACP
TL431IP
TL431AIP
CATHODEANODE
SOT-89
(PK)
TL431CPK TL431CPW
TL431IPK
SHRINK
SMALL
OUTLINE
(PW)
CHIP
FORM
(Y)
equivalent schematic
CATHODE
REF
†
2.4 kΩ
3.28 kΩ
7.2 kΩ
REF
V
ref
CATHODE
ANODE
20 pF
+
_
800 Ω
4 kΩ
800 Ω
20 pF
150 Ω
10 kΩ
ANODE
†
All component values are nominal.
2
1 kΩ
800 Ω
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Operating free-air temperature range, T
°C
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, θ
(see Notes 2 and 3): D package 97°C/W. . . . . . . . . . . . . . . . . . . . . . . . . . . .
JA
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, T
†
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),
ambient temperature is PD = (TJ(max) – TA)/
3. The package thermal impedance is calculated in accordance with JESD 51, except for through-hole packages, which use a trace
length of zero.
–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
stg
θ
, and TA. The maximum allowable power dissipation at any allowable
θ
JA
JA
. Operating at the absolute maximum TJ of 150°C can impact reliability.
recommended operating conditions
MIN MAX UNIT
Cathode voltage, V
Cathode current, I
p
KA
KA
p
A
TL431C, TL431AC 0 70
TL431I, TL431AI –40 85
V
ref
36 V
1 100 mA
°
†
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
3
TL431, TL431A
PARAMETER
TEST CONDITIONS
UNIT
ref
gg
3
I
mA
mV
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
TL431C
MIN TYP MAX
4 25 mV
–1.4 –2.7
V
0.4 1.2 µA
0.4 1 mA
0.2 0.5 Ω
V
ref
V
I(dev)
D
V
D
V
I
ref
I
I(dev)
I
min
I
off
|zKA| Dynamic impedance (see Figure 1) 1
†
Full range is 0°C to 70°C for the TL431C.
Reference voltage 2 VKA = V
Deviation of reference voltage
over full temperature range
(see Figure 1)
Ratio of change in reference voltage
to the change in cathode voltage
KA
Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
over full temperature range
(see Figure 1)
Minimum cathode current
for regulation
Off-state cathode current 4 VKA = 36 V, V
TEST
CIRCUIT
2
3
2 VKA = V
, IKA = 10 mA 2440 2495 2550 mV
ref
VKA = V
TA = full range
= 10
KA
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range
IKA = 1 mA to 100 mA, VKA = V
f ≤ 1 kHz
ref, IKA
ref
= 10 mA,
†
∆VKA = 10 V – V
∆VKA = 36 V – 10 V –1 –2
†
= 0 0.1 1 µA
ref
ref
ref
,
The deviation parameters V
ref(dev)
and I
ref(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, α
Ť
a
Vref
ppm
Ť
ǒ
°C
, is defined as:
Vref
ǒ
V
Ǔ
+
V
ref
)
I(dev
at 25°C
D
T
A
10
6
Minimum V
Ǔ
Maximum V
ref
ref
∆T
V
I(dev)
A
where:
∆TA is the recommended operating free-air temperature range of the device.
α
can be positive or negative, depending on whether minimum V
Vref
or maximum V
ref
, respectively , occurs at the
ref
lower temperature.
Example: maximum V
= 2496 mV at 30°C, minimum V
ref
= 2492 mV at 0°C, V
ref
= 2495 mV at 25°C,
ref
∆TA = 70°C for TL431C
4mV
ǒ
Ť
+
2495 mV
Ť
a
Vref
Because minimum V
Ǔ
70°C
occurs at the lower temperature, the coefficient is positive.
ref
Calculating Dynamic Impedance
The dynamic impedance is defined as:
10
6
[
23 ppmń°C
Ť
Ť
z
+
KA
D
V
KA
D
I
KA
When the device is operating with two external resistors (see Figure 3), the total dynamic impedance of the circuit
is given by:
D
|
z
Ȁ|+
V
[Ťz
D
I
KA
Ť
R1
ǒ
1
)
R2
Ǔ
4
Figure 1. Calculating Deviation Parameters and Dynamic Impedance
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PARAMETER
TEST CONDITIONS
UNIT
ref
gg
3
I
mA
mV
PARAMETER
TEST CONDITIONS
UNIT
ref
gg
3
I
mA
mV
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
TL431I
MIN TYP MAX
5 50 mV
–1.4 –2.7
V
0.8 2.5 µA
0.4 1 mA
0.2 0.5 Ω
V
ref
V
I(dev)
D
V
D
V
I
ref
I
I(dev)
I
min
I
off
|zKA| Dynamic impedance (see Figure 1) 2
†
Full range is –40°C to 85°C for the TL431I.
Reference voltage 2 VKA = V
Deviation of reference voltage
over full temperature range
(see Figure 1)
Ratio of change in reference voltage
to the change in cathode voltage
KA
Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
over full temperature range
(see Figure 1)
Minimum cathode current for
regulation
Off-state cathode current 4 VKA = 36 V, V
TEST
CIRCUIT
2
3
2 VKA = V
, IKA = 10 mA 2440 2495 2550 mV
ref
VKA = V
TA = full range
= 10
KA
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range
IKA = 1 mA to 100 mA, VKA = V
f ≤ 1 kHz
ref, IKA
ref
= 10 mA,
†
∆VKA = 10 V – V
∆VKA = 36 V – 10 V –1 –2
†
= 0 0.1 1 µA
ref
ref
ref
,
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
TL431AC
MIN TYP MAX
4 25 mV
–1.4 –2.7
V
0.8 1.2 µA
0.4 0.6 mA
0.2 0.5 Ω
V
ref
V
I(dev)
D
V
D
V
I
ref
I
I(dev)
I
min
I
off
|zKA| Dynamic impedance (see Figure 1) 1
‡
Full range is 0°C to 70°C for the TL431AC.
Reference voltage 2 VKA = V
Deviation of reference voltage
over full temperature range
(see Figure 1)
Ratio of change in reference voltage
to the change in cathode voltage
KA
Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
over full temperature range
(see Figure 1)
Minimum cathode current
for regulation
Off-state cathode current 4 VKA = 36 V, V
TEST
CIRCUIT
2
3
2 VKA = V
, IKA = 10 mA 2470 2495 2520 mV
ref
VKA = V
TA = full range
= 10
KA
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range
IKA = 1 mA to 100 mA, VKA = V
f ≤ 1 kHz
ref, IKA
ref
= 10 mA,
†
∆VKA = 10 V – V
∆VKA = 36 V – 10 V –1 –2
‡
= 0 0.1 0.5 µA
ref
ref
ref
,
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
5
TL431, TL431A
PARAMETER
TEST CONDITIONS
UNIT
ref
gg
3
I
mA
mV
PARAMETER
TEST CONDITIONS
UNIT
ref
gg
3
I
mA
mV
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
TL431AI
MIN TYP MAX
5 50 mV
–1.4 –2.7
V
0.8 2.5 µA
0.4 0.7 mA
0.2 0.5 Ω
V
ref
V
I(dev)
D
V
D
V
I
ref
I
I(dev)
I
min
I
off
|zKA| Dynamic impedance (see Figure 1) 2
†
Full range is –40°C to 85°C for the TL431AI.
Reference voltage 2 VKA = V
Deviation of reference voltage
over full temperature range
(see Figure 1)
Ratio of change in reference voltage
to the change in cathode voltage
KA
Reference current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 4 µA
Deviation of reference current
over full temperature range
(see Figure 1)
Minimum cathode current
for regulation
Off-state cathode current 4 VKA = 36 V, V
TEST
CIRCUIT
2
3
2 VKA = V
, IKA = 10 mA 2470 2495 2520 mV
ref
VKA = V
TA = full range
= 10
KA
IKA = 10 mA, R1 = 10 kΩ, R2 = ∞,
TA = full range
IKA = 1 mA to 100 mA, VKA = V
f ≤ 1 kHz
ref, IKA
ref
= 10 mA,
†
∆VKA = 10 V – V
∆VKA = 36 V – 10 V –1 –2
†
= 0 0.1 0.5 µA
ref
ref
ref
,
electrical characteristics over recommended operating conditions, TA = 25°C (unless otherwise
noted)
TEST
CIRCUIT
V
ref
D
V
D
V
I
ref
I
min
I
off
|zKA| Dynamic impedance
‡
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:
|zȀ|
Reference voltage 2 VKA = V
Ratio of change in reference voltage
to the change in cathode voltage
KA
Reference input current 3 IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ 2 µA
Minimum cathode current
for regulation
Off-state cathode current 4 VKA = 36 V, V
‡
D
V
KA
Ť
+
D
I
KA
+
∆V
∆I
[
|zKA|ǒ1
)
R1
R2
Ť
z
KA
Ǔ
KA
2 VKA = V
IKA = 1 mA to 100 mA, VKA = V
2
f ≤ 1 kHz
, IKA = 10 mA 2495 mV
ref
= 10
ref
∆VKA = 10 V – V
∆VKA = 36 V – 10 V –1
= 0 0.1 µA
ref
ref
ref
,
TL431Y
MIN TYP MAX
–1.4
V
0.4 mA
0.2 Ω
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
PARAMETER MEASUREMENT INFORMATION
Input V
V
ref
I
KA
KA
Figure 2. Test Circuit for VKA = V
I
KA
VKA+
V
KA
ǒ
V
ref
Input
R1
R2
I
ref
V
ref
Figure 3. Test Circuit for VKA > V
ref
R1
Ǔ
1
)
)
I
R1
ref
R2
ref
I
V
off
Input
Figure 4. Test Circuit for I
KA
off
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
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
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
Voltage monitor 26
Delay timer 27
Precision current limiter 28
Precision constant-current sink 29
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
REFERENCE VOLTAGE
vs
FREE-AIR TEMPERATURE
2600
VKA = V
2580
IKA = 10 mA
2560
2540
2520
2500
2480
– Reference Voltage – mV
2460
ref
V
2440
2420
2400
–75 –50 –25 0 25 50 75
‡
Data is for devices having the indicated value of V
TA = 25°C.
ref
V
= 2550 mV
ref
V
ref
TA – Free-Air Temperature – °C
TYPICAL CHARACTERISTICS
‡
= 2495 mV
V
= 2440 mV
ref
at IKA = 10 mA,
ref
‡
‡
100 125
5
4
Aµ
3
2
– Reference Current –ref
I
1
0
–75 –25 0 50
†
REFERENCE CURRENT
vs
FREE-AIR TEMPERATURE
R1 = 10 kΩ
R2 = ∞
IKA = 10 mA
–50 25 75
TA – Free-Air Temperature – °C
100 125
CATHODE CURRENT
CATHODE VOLTAGE
150
VKA = V
125
TA = 25°C
100
75
50
25
0
– Cathode Current – mAI
–25
KA
–50
–75
–100
–2 –1 0 1
ref
VKA – Cathode Voltage – V
Figure 5
Figure 7
vs
23
800
VKA = V
TA = 25°C
600
Aµ
400
200
– Cathode Current –
KA
I
0
–200
–1 0 1
ref
Figure 6
CATHODE CURRENT
vs
CATHODE VOLTAGE
I
min
VKA – Cathode Voltage – V
Figure 8
23
†
Data at high and low temperatures are applicable only within the recommended operating free-air temperature ranges of the various devices.
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9
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
OFF-STATE CATHODE CURRENT
FREE-AIR TEMPERATURE
2.5
VKA = 36 V
V
= 0
ref
2
1.5
1
– Off-State Cathode Current –
0.5
off Aµ
I
0
–50 25 75
–75 –25 0 50
TA – Free-Air Temperature – °C
vs
TYPICAL CHARACTERISTICS
RATIO OF DELTA REFERENCE VOLTAGE TO
– 0.85
– 0.95
–1.05
– mV/V
KA
–1.15
∆V
/
ref
–1.25
∆V
–1.35
–1.45
100 125
–75 –25 0 50 100 125–50 25 75
†
DELTA CATHODE VOLTAGE
vs
FREE-AIR TEMPERATURE
VKA = 3 V to 36 V
TA – Free-Air Temperature – °C
Figure 9
– Equivalent Input Noise Voltage – nV/ HzV
n
EQUIVALENT INPUT NOISE VOLTAGE
vs
FREQUENCY
260
IO = 10 mA
TA = 25°C
240
220
200
180
160
140
120
100
10 100 1 k
f – Frequency – Hz
Figure 11
Figure 10
10 k 100 k
†
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
6
5
4
3
2
1
0
–1
–2
–3
f = 0.1 to 10 Hz
–4
– Equivalent Input Noise voltage – µV
19.1 V
n
V
IKA = 10 mA
–5
TA = 25°C
–6
0123456
t – Time – s
78910
500 µF
1 kΩ
910 Ω
2000 µF
V
TL431
(DUT)
820 Ω
16 Ω
0.1 µF
160 kΩ
CC
TLE2027
AV = 10 V/mV
+
–
V
EE
16 kΩ 16 kΩ
1 µF
1 µF
33 kΩ
Figure 12. Test Circuit for Equivalent Input Noise Voltage
33 kΩ
V
CC
+
–
V
EE
TLE2027
AV = 2 V/V
To Oscilloscope
22 µF
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11
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
TYPICAL CHARACTERISTICS
SMALL-SIGNAL VOLTAGE AMPLIFICATION
vs
FREQUENCY
60
IKA = 10 mA
TA = 25°C
50
40
30
9 µF
15 kΩ
8.25 kΩ
I
KA
Output
232 Ω
+
–
20
10
– Small-Signal Voltage Amplification – dBA
V
0
1 k 10 k 100 k 1 M 10 M
f – Frequency – Hz
REFERENCE IMPEDANCE
vs
FREQUENCY
100
IKA = 10 mA
TA = 25°C
10
1
– Reference Impedance –
KA
|z | Ω
Figure 13
GND
TEST CIRCUIT FOR VOLTAGE AMPLIFICATION
1 kΩ
50 Ω
–
+
TEST CIRCUIT FOR REFERENCE IMPEDANCE
Output
I
KA
GND
12
0.1
1 k 10 k 100 k 1 M 10 M
f – Frequency – Hz
Figure 14
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
5
4
3
Input
Output
Pulse
Generator
f = 100 kHz
220 Ω
Output
50 Ω
2
Input and Output Voltage – V
1
0
–1 0 1 2 3 4
t – Time – µs
567
Figure 15
STABILITY BOUNDARY CONDITIONS
100
A VKA = V
B VKA = 5 V
90
C VKA = 10 V
D VKA = 15 V
80
70
60
50
40
– Cathode Current – mA
30
KA
I
20
10
0
0.001 0.01 0.1 1
†
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. V
CL were then adjusted to determine the ranges of stability.
ref
f
B
Stable
A
CL – Load Capacitance – µF
C
D
†
TA = 25°C
Stable
BATT
10
and
GND
TEST CIRCUIT FOR PULSE RESPONSE
150 Ω
I
KA
+
C
L
TEST CIRCUIT FOR CURVE A
I
R1 = 10 kΩ
C
L
R2
TEST CIRCUIT FOR CURVES B, C, AND D
V
–
KA
+
–
BATT
150 Ω
V
BATT
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
I(BATT)
(see Note A)
V
ref
Figure 17. Shunt Regulator
R1
0.1%
R2
0.1%
V
I(BATT)
V
RETURN
NOTE A: R should provide cathode current ≥1 mA to the TL431 at minimum V
TL431
I(BATT)
V
O
R1
VO+ǒ1
.
)
R2
Ǔ
V
ref
TL431
Input
VIT ≈ 2.5 V
Von ≈ 2 V
V
Figure 18. Single-Supply Comparator With Temperature-Compensated Threshold
V
I(BATT)
TL431
NOTE A: R should provide cathode current ≥1 mA to the TL431 at minimum V
R
(see Note A)
30 Ω
0.01 µF
R2
0.1%
2N222
4.7 kΩ
R1
0.1%
Figure 19. Precision High-Current Series Regulator
V
O
≈ V
off
GND
I(BATT)
I(BATT)
2N222
V
.
R1
V
+ǒ1
O
O
)
R2
Ǔ
V
ref
14
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
APPLICATION INFORMATION
V
I(BATT)
Common
TL431
Figure 20. Output Control of a Three-Terminal Fixed Regulator
IN
uA7805
OUT
R2
R1
V
O
V
Minimum VO+
O
+ǒ1
)
R1
R2
Ǔ
V
ref
V
)
5V
ref
V
I(BATT)
R2
R1
TL431
V
O
VO+ǒ1
)
Figure 21. High-Current Shunt Regulator
V
I(BATT)
R1
TL431
C
R2
NOTE A: Refer to the stability boundary conditions in Figure 16 to determine allowable values for C.
(see Note A)
Figure 22. Crowbar Circuit
R1
R2
Ǔ
V
ref
V
O
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
15
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
APPLICATION INFORMATION
V
I(BATT)
IN OUT
LM317
8.2 kΩ
TL431
Adjust
243 Ω
0.1%
243 Ω
0.1%
Figure 23. Precision 5-V 1.5-A Regulator
V
I(BATT)
R
(see Note A)
b
27.4 kΩ
0.1%
TL431
27.4 kΩ
0.1%
VO ≈ 5 V, 1.5 A
VO ≈ 5 V
NOTE A: Rb should provide cathode current ≥1-mA to the TL431.
Figure 24. Efficient 5-V Precision Regulator
6.8 kΩ
5 V
TL431
10 kΩ
10 kΩ
0.1%
10 kΩ
0.1%
Feedback
Figure 25. PWM Converter With Reference
Not
Used
12 V
V
CC
–
+
X
TL598
16
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TL431, TL431A
ADJUSTABLE PRECISION SHUNT REGULATORS
SLVS005J – JULY 1978 – REVISED JULY 1999
APPLICATION INFORMATION
R3
V
I(BATT)
R1A
TL431
(see Note A)
R1B
R2BR2A
R4
(see Note A)
R1B
ǒ
Low Limit
High Limit
LED on When Low Limit < V
+
+ǒ1
1
)
)
R2B
R1A
R2A
Ǔ
V
Ǔ
V
ref
ref
I(BATT)
< High Limit
NOTE A: R3 and R4 are selected to provide the desired LED intensity and cathode current ≥1 mA to the TL431 at the available V
Figure 26. Voltage Monitor
12 V
Off
650 Ω
On
2 kΩ
TL431
C
Delay+R C I
ǒ
n
12 V*V
12 V
Ǔ
ref
R
Figure 27. Delay Timer
V
I(BATT)
R
0.1%
R1
TL431
CL
I
O
V
ref
I
+
)
R
I
h
CL
V
I(BATT
O
FE
)
I
KA
)
I
KA
out
R1
+
I(BATT)
.
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
V
I(BATT)
TL431
Figure 29. Precision Constant-Current Sink
I
O
R
S
0.1%
V
ref
I
+
O
R
S
18
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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