©2011 Fairchild Semiconductor Corporation
Rev. 1.0.6
February 2011
Features
• Programmable Output Voltage to 36 Volts
• Low Dynamic Output Impedance 0.2Ω Typical
• Sink Current Capability of 1.0 to 100mA
• Equivalent Full-Range Temperature Coefficient of
50ppm/°C Typical
• Temperature Compensated for Operation Over Full Rated
Operating Temperature Range
• Low Output Noise Voltage
• Fast T urn-on Response
Description
The LM431SA/LM431SB/LM431SC are three terminal
output adjustable regulators with thermal stability over
operating temperature range. The output voltage can be set
any value between VREF (approximately 2.5 volts) and 36
volts with two external resistors. These devices have a
typical dynamic output impedance of 0.2Ω. Active output
circuit provides a sharp turn-on characte ristic, making these
devices excellent replacement for Zener Diodes in many
applications.
SOT-23F
12
3
1. Cathode 2. Ref 3. Anode
1. Ref 2. Anode 3. Cathode
1
SOT-89
Internal Block Diagram
+
-
LM431SA/LM431SB/LM431SC
Programmable Shunt Regulator
LM431SA/LM431SB/LM431SC
2
Absolute Maximum Ratings
(Operating temperature range applies unless otherwise specified.)
Note:
1. Thermal resistance test board
Size: 76.2mm * 114.3mm * 1.6mm (1S0P)
JEDEC Standard: JESD51-3, JESD51-7
2. Assume no ambient airflow.
3. TJMAX = 150°C, Ratings apply to ambient temperature at 25°C
4. Power dissipation calculation: PD = (TJ - TA)/RθJA
Recommended Operating Conditions
Parameter Symbol Value Unit
Cathode Voltage VKA 37 V
Cathode current Range (Continuous) IKA -100 ~ +150 mA
Reference Input Current Range IREF -0.05 ~ +10 mA
Thermal Resistance Junction-Air (Note1,2)
MF Suffix Package
ML Suffix Package RθJA 350
220 °C/W
Power Dissipation (Note3,4)
MF Suffix Package
ML Suffix Package PD350
560 mW
Junction Temperature TJ150 °C
Operating Temperature Range TOPR -25 ~ +85 °C
Storage Temperature Range TSTG -65 ~ +150 °C
Parameter Symbol Min. Typ. Max. Unit
Cathode Voltage VKA VREF -36V
Cathode Current IKA 1.0 - 100 mA
LM431SA/LM431SB/LM431SC
3
Electrical Characteristics
(TA = +25°C, unless otherwise specified)
Note1
TMIN = -25°C, TMAX = +85°C
Parameter Symbol Conditions LM431SA LM431SB LM431SC Unit
Min. Typ. Max. Min. Typ. Max. Min. Typ. Max.
Reference
Input Voltage VREF VKA=VREF, IKA=10mA 2.450 2.500 2.550 2.470 2.495 2.520 2.482 2.495 2.508 V
Deviation of
Reference
Input Voltage
Over-
Temperature
Δ
VREF/
Δ
TVKA=VREF, IKA=10mA
TMIN≤TA≤TMAX - 4.5 17 - 4.5 17 - 4.5 17 mV
Ratio of
Change in
Reference
Input Voltage
to the Change
in Cathode
Voltage
Δ
VREF/
Δ
VKA IKA
=10mA
Δ
VKA=10V-
VREF - -1.0 -2.7 - -1.0 -2.7 - -1.0 -2.7
mV/V
Δ
VKA=36V-
10V - -0.5 -2.0 - -0.5 -2.0 - -0.5 -2.0
Reference
Input Current IREF IKA=10mA,
R1=10KΩ,R2=∞- 1.5 4 - 1.5 4 - 1.5 4
μ
A
Deviation of
Reference
Input Current
Over Full
Temperature
Range
Δ
IREF/
Δ
T
IKA=10mA,
R1=10KΩ,R2=∞
TA =Full Range - 0.4 1.2 - 0.4 1.2 - 0.4 1.2
μ
A
Minimum
Cathode
Current for
Regulation
IKA(MIN) VKA=VREF - 0.45 1.0 - 0.45 1.0 - 0.45 1.0 mA
Off -Stage
Cathode
Current IKA(OFF) VKA=36V, VREF=0 - 0.05 1.0 - 0.05 1.0 - 0.05 1.0
μ
A
Dynamic
Impedance ZKA VKA=VREF,
IKA=1 to 100mA ,f ≥1.0kHz - 0.15 0.5 - 0.15 0.5 - 0.15 0.5 Ω
LM431SA/LM431SB/LM431SC
4
Test Circuits
Figure 1. Test Circuit for VKA=VREF Figure 2. Test Circuit for VKA≥VREF
LM431S
LM431S
LM431S
Figure 3. Test Circuit for lKA(OFF)
LM431SA/LM431SB/LM431SC
5
Typical Performance Characteristics
-2 -1 0 1 2 3
-100
-50
0
50
100
150
VKA = VREF
TA = 25oC
IK, Cathode Current (mA)
VKA, Cathode Voltage (V)
-50 -25 0 25 50 75 100 125
0.000
0.025
0.050
0.075
0.100
Ioff, Off-State Cathode Current (uA)
TA, Ambient Temperature (oC)
1k 10k 100k 1M 10M
-10
0
10
20
30
40
50
60
TA = 25oC
IKA = 10mA
Open Loop Voltage Gain (dB)
Frequency (Hz)
-10123
-200
0
200
400
600
800
IKA(MIN)
VKA = VREF
TA = 25oC
IKA, CATHODE CURRENT (uA)
VKA, CATHODE VOLTAGE (V)
-50 -25 0 25 50 75 100 125
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Iref, Reference Input Current (uA)
TA, Ambient Temperature (oC)
0 4 8 12 16 20
0
1
2
3
4
5
6
TA=25oC
OUTPUT
INPUT
Voltage Swing (V)
Time (us)
Figure 4. Cathode Current vs. Cathode Voltage Figure 5. Cathode Current vs. Cathode Voltage
Figure 6. OFF-State Cathode Current vs.
Ambient Temperature Figure7. Reference Input Current vs.
Ambient Temperature
Figure 8. Small Signal Voltage Amplification vs. Frequency Figure 9. Pulse Response
LM431SA/LM431SB/LM431SC
6
Typical Performance Characteristics (Continued)
Figure 10. Stability Boundary Conditions Figure 11. Anode-Reference Diode Curve
Figure 12. Reference-Cathode Diode Curve
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
0
1
2
3
4
5
Current(mA)
Anode-Ref. Voltage(V)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
0
1
2
3
4
5
Current(mA)
Ref.-Cathode Voltage(V)
100p 1n 10n 100n 1
ٛ
10
ٛ
0
20
40
60
80
100
120
140
B
A
A V
KA
= Vref
B V
KA
= 5.0 V @ I
K
= 10
mA
T
A
= 25
o
C
I
K
, CATHODE CURRENT(mA)
C
L
, LOAD CAPACITANCE
stable stable
LM431SA/LM431SB/LM431SC
7
Typical Application
VO1R1
R2
-------
+
⎝⎠
⎛⎞
Vref
=
LM431S
VOVref 1R1
R2
-------
+
⎝⎠
⎛⎞
=
LM431S
LM7805/MC7805
VO1R1
R2
-------
+
⎝⎠
⎛⎞
Vref
=
LM431S
LM431S LM431S
Figure 13. Shunt Regulator Figure 14. Output Control for
-Three-Termianl Fixed Regulator Figure 15. High Current Shunt Regulator
Figure 16. Current Limit or Current Source Figure 17. Constant-Current Sink
LM431SA/LM431SB/LM431SC
8
Mechanical Dimensions
Package Dimensions in millimeters
Marking
SOT-23F
43A 43B 43C
2% tolerance 1% tolerance 0.5% tolerance
LM431SA/LM431SB/LM431SC
9
Mechanical Dimensions (Continued)
Package Dimensions in millimeters
Marking
SOT-89
0.40
±0.10
2.50
±0.20
(0.50)
(0.40
)
4.10
±0.20
0.40
+0.10
–0.05
0.50
±0.10
1.65
±0.10
4.50
±0.20
1.50
±0.20
C0.2
1.50 TYP 1.50 TYP
(1.10)
43A
2% tolerance 1% tolerance 0.5% tolerance
43B 43C
LM431SA/LM431SB/LM431SC
10
Ordering Information
Product Number Output Voltage Tolerance Package Operating Temperature
LM431SCCML 0.5% SOT-89
-25 ~ +85°C
LM431SCCMF SOT-23F
LM431SBCML 1% SOT-89
LM431SBCMF SOT-23F
LM431SACML 2% SOT-89
LM431SACMF SOT-23F
LM431SA/LM431SB/LM431SC
2/22/11 0.0m 001
Stock#DS400507
© 2011 Fairchild Semiconductor Corporation
www.fairchildsemi.com
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IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE
OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN;NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE
RIGHTS OF OTHERS. THESE SPECIFICATIONS DO NOT EXPAND THE TERMS OF F AIRCHILD’S WORLDWIDE TERMS AND CONDITIONS, SPE-
CIFICALLY THE WARRANTY THEREIN, WHICH COVERS THESE PRODUCTS.
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FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITIC AL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WIT HOUT
THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION.
As used herein:
1. Life support devices or systems are devices or systems which, (a) are
intended for su rgical impla nt into th e body, or (b) support or su stain life , or
(c) whose failure to perform when properly used in accordance with
instructions for use provided in the labeling, can be reasonably expected
to result in significant injury to the user.
2. A critical component is any component of a life support device or system
whose failure to perform can be reasonably expected to cause the failure
of the life support device or system, or to affect its safety or ef fectiveness.
PRODUCT STATUS DEFINITIONS
Definition of Terms
Datasheet Identification Product Status Definition
Advance Information Formative or In Design This datasheet contains the design specifications for
product development. Specifications may change in
any manner withou t notice.
Preliminary First Production This datasheet contains preliminary data, and
supplementary data will be published at a later date.
Fairchild Semiconductor reserves the right to make
changes at any time without notice in order to improve
design.
No Identification Needed Full Production This datasheet contains final specifications. Fairchild
Semiconductor reserves the right to make changes at
any time without notice in order to improve design.
Obsolet e Not In Prod uction This datashee t contains specifications on a product
that has been discontinued by Fairchild s emi conductor.
The datasheet is printed for reference information only.
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