LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 1
August 2013
LM431SA / LM431SB / LM431SC
Programmable Shunt Regulator
Features
• Programmable Output Voltage to 36 V
• Low Dynamic Output Impedance: 0.2 Ω (Typical)
• Sink Current Capability of 1.0 to 100 mA
• Equivalent Full-Range Temperature Coefficient of
50 ppm/°C(Typical)
• Temperature Compensated for Operation Over Full
Rated Operating Temperature Range
• Low Output Noise Voltage
• Fast Turn-on Response
Ordering Information
Product Number Output V oltage
Tolerance Operating
Temperature Top Mark Package Packing Method
LM431SACMFX 2%
-25 to +85°C
43A SOT-23F 3L
Ta pe and Reel
LM431SACM3X 43L SOT-23 3L
LM431SACM32X 43G SOT-23 3L
LM431SBCMLX
1%
43B SOT-89 3L
LM431SBCMFX 43B SOT-23F 3L
LM431SBCM3X 43M SOT-23 3L
LM431SBCM32X 43H SOT-23 3L
LM431SCCMLX
0.5%
43C SOT-89 3L
LM431SCCMFX 43C SOT-23F 3L
LM431SCCM3X 43N SOT-2 3 3L
LM431SCCM32X 43J SOT-23 3L
LM431SAIMFX 2% -40 to +85°C 43AI SOT-23F 3L
1. Ref 2. Anode 3. Cathode
1
SOT-89 SOT-23F
12
3
1. Cathode 2. Ref 3. Anode
SOT-23
12
3
M32 - 1. Ref 2. Cathode 3. Anode
M3 - 1. Cathode 2. Ref 3. Anode
Description
The LM431SA / LM431SB / LM431SC are three-terminal
the output adjustable regulators with thermal stability
over operating temperature range. The output voltage
can be set any value between VREF (approximately 2.5
V) and 36 V with two external resistors. These devices
have a typica l dyna mic o utput imp edanc e of 0.2 Ω. Active
output circuit provides a sharp turn-on characteristic,
making these devices excellent replacement for Zener
diodes in many applications.
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 2
Block Diagram
Figure 1. Block Diagram
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be opera-
ble above the re co mmen ded operating conditions an d s tres si ng the parts to the se lev el s i s n ot re co mme nded. In addi-
tion, extended exposure to stresses above the recommended operating conditions may affect device reliability. The
absolute maximum ratings are stress ratings only. Values are at TA = 25°C unless otherwise noted.
Notes:
1. Thermal resistance test board
Size: 1.6 mm x 76 .2 mm x 114.3 mm (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
Symbol Parameter Value Unit
VKA Cathode Voltage 37 V
IKA Cathode current Range (Continuous) -100 to +150 mA
IREF Reference Input Current Range -0.05 to +10.00 mA
RθJA Thermal Resistance
Junction-Air (1,2)
ML Suffix Package (SOT-89) 220
°C/WMF Suffix Package (SOT-23F) 350
M32, M3 Suffix Package (SOT-23) 400
PDPower Dissipation (3,4) ML Suffix Package (SOT-89) 560 mWMF Suffix Package (SOT-23F) 350
M32, M3 Suffix Package (SOT-23) 310
TJJunction Temperature 150 °C
TOPR Operating Temperature
Range All products except LM431SAIMFX -25 to +85 °C
LM431SAIMFX -40 to +85
TSTG Storage Tem perature Range -65 to +150 °C
Symbol Parameter Min. Max. Unit
VKA Cathode Voltage VREF 36 V
IKA Cathode Current 1 100 mA
+
-
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 3
Electrical Characteristics
Values are at TA = 25°C unless otherwise noted.
Note:
5. TMIN = -25°C, TMAX = +85°C.
Symbol Parameter Conditions LM431SA LM431SB LM431SC Unit
Min. Typ. Max. Min. Typ. Max. Min. Typ. Max.
VREF Reference
Input Voltage VKA = VREF, IKA = 10 mA 2.450 2.500 2.550 2.470 2.495 2.520 2.482 2.495 2.508 V
Δ
VREF /
Δ
T
Deviation of
Reference
Input Voltage
Over-
Temperature
VKA = VREF,
IKA = 10 mA
TMIN ≤ TA ≤
TMAX
SOT-89
SOT-23F 4.5 17.0 4.5 17.0 4.5 17.0 mV
SOT-23 6.6 24 6.6 24 6.6 24 mV
Δ
VREF /
Δ
VKA
Ratio of
Change in
Reference
Input Voltage
to the Change
in Cathode
Voltage
IKA =10 mA
Δ
VKA =
10 V-VREF -1.0 -2.7 -1.0 -2.7 -1.0 -2.7
mV/V
Δ
VKA =
36 V-10 V -0.5 -2.0 -0.5 -2.0 -0.5 -2.0
IREF Reference
Input Current IKA = 10 mA,
R1 = 10 KΩ, R2 = ∞1.5 4.0 1.5 4.0 1.5 4.0 μA
Δ
IREF /
Δ
T
Deviation of
Reference
Input Current
Over Full
Temperature
Range
IKA = 10 mA,
R1 = 10 KΩ,
R2 = ∞,
TA =
Full Range
SOT-89
SOT-23F 0.4 1.2 0.4 1.2 0.4 1.2 μA
SOT-23 0.8 2.0 0.8 2.0 0.8 2.0 μA
IKA(MIN)
Minimum
Cathode
Current for
Regulation
VKA = VREF 0.45 1.00 0.45 1.00 0.45 1.00 mA
IKA(OFF)
Off -Stage
Cathode
Current VKA = 36 V, VREF = 0 0.05 1.00 0.05 1.00 0.05 1.00 μA
ZKA Dynamic
Impedance
VKA = VREF,
IKA = 1 to 100 mA,
f ≥ 1.0 kHz 0.15 0.50 0.15 0.50 0.15 0.50 Ω
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 4
Electrical Characteristics(6, 7) (Continued)
Values are at TA = 25°C unless otherwise noted.
Notes:
6. TMIN = -40°C, TMAX = +85°C.
7. The devi ation paramet ers VREF(dev) and IREF(dev)are defined as the diff erences between the maximum and minimum
values obtained over the rated temperature range. The average full-range temperature coefficient of the reference
input voltage, αVREF, is defined as:
where TMAX -TMIN is the rated operating free-air temperature range of the device.
αVREF can be positive or ne gative, dependi ng on whether mini mum VREF or maximum VREF, respectivel y, occurs at
the lower temperature.
Example: VREF(dev) = 4.5 mV, VREF = 2500 mV at 25 °C, TMAX -TMIN = 125 °C for LM431SAI.
Because minimum VREF occurs at the lower temperature, the coefficient is positive.
Symbol Parameter Conditions LM431SAI Unit
Min. Typ. Max.
VREF Reference Input Voltage VKA = VREF, IKA = 10 mA 2.450 2.500 2.550 V
VREF(dev)
Deviation of Reference
Input Voltage Over-
Temperature
VKA = VREF, IKA = 10 mA,
TMIN ≤ TA ≤ TMAX 520mV
Δ
VREF/
Δ
VKA
Ratio of Change in
Reference Input Voltage
to Change in Cathode
Voltage
IKA = 10 mA
Δ
VKA = 10 V - VREF -1.0 -2.7
mV/V
Δ
VKA = 36 V - 10 V -0.5 -2.0
IREF Reference Input Current IKA = 10 mA, R1 =10 KΩ, R2 = ∞1.5 4.0 μA
IREF(dev)
Deviation of Reference
Input Current Over Full
Temperature Range
IKA = 10 mA, R1 = 10 KΩ, R2 = ∞,
TMIN ≤ TA ≤ TMAX 0.8 2.0 μA
IKA(MIN) Minimum Cathode
Current for Regulation VKA = VREF 0.45 1.00 mA
IKA(OFF) Off -Stage Cathode
Current VKA = 36 V, VREF = 0 0.05 1 .00 μA
ZKA Dynamic Impedance VKA = VREF, IKA = 1 to 100 mA,
f ≥ 1.0 kHz 0.15 0.50 Ω
αVREF ppm
°C
------------


VREF dev()
VREF at25°C()
----------------------------------------


106
⋅
TMAX TMIN
–
------------------------------------------------------------
=
αVREF
4.5mV
2500mV
------------------------


106
⋅
125°C
-------------------------------------------- 14.4ppm °C⁄==
V
REF(min)
V
REF(max)
T
MAX
-T
MIN
V
REF(dev)
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 5
Test Circuits
Figure 2. Test Circuit for VKA = VREF Figure 3. Test Circuit for VKA ≥ VREF
Figure 4. Test Circuit for lKA(OFF)
LM431S
LM431S
LM431S
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 6
Typical Performance Characteristics
Figure 5. Cathode Current vs. Cathode Voltage Figure 6. Cathode Current vs. Cathode Voltage
Figure 7. OFF-State Cathode Current vs.
Ambient Temperature Figure 8. Reference Input Current vs.
Ambient Temperature
Figure 9. Frequency vs. Small Signal Voltage
Amplification Figure 10. Pulse Response
-2 -1 0 1 2 3
-100
-50
0
50
100
150
VKA = VREF
TA = 25oC
IK, Cathode Current ( m A)
VKA, Cathode Voltage (V)
-50 -25 0 25 50 75 100 125 150
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Ioff, Off-State Cathode Current (uA)
TA, Am bient Temperature (oC)
-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)
1k 10k 100k 1M 10M
-10
0
10
20
30
40
50
60
TA = 25oC
IKA = 10mA
Open Loop Voltage Gain (dB )
Frequency (Hz)
048121620
0
1
2
3
4
5
6
TA=25oC
OUTPUT
INPUT
Voltage Swing (V)
Time (us)
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 7
Typical Performance Characteristics (Continued)
Figure 11. Stability Boundary Conditions Figure 12. Anode-Reference Diode Curve
Figure 13. Reference-Cathode Diode Curve Figure 14. Reference Input Voltage vs. Ambient Tem-
perature
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
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)
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 8
Typical Application
Figure 15. Shunt Regulator Figure 16. Output fir Three-Terminal Fixed Regulator
Figure 17. High Current Shunt Regulator
Figure 18. Current Limit or Current Source Figure 19. Constant-Current Sink
VO1R1
R2
-------
+


Vref
=
LM431S
VOVref 1R1
R2
-------
+


=
LM431S
LM7805/MC7805
VO1R1
R2
-------
+


Vref
=
LM431S
LM431S
LM431S
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 9
Physical Dimensions
Figure 20. 3-LEAD, SOT-89, JEDEC TO-243, OPTION AA (ACTIVE)
Package drawings are provided as a service to customers considering Fairchild components. Drawings may c hange in any manner
without notic e. Please note the revision and/or date on the drawing and contact a Fairchild Sem iconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the
warranty therein, which covers Fairchild produ cts.
Always visit Fairchild Semiconduct or’s online packaging are a for the most recent package drawings :
http://www.fairchildsemi.com/dwg/MA/MA03C.pdf.
For current tape an d reel specifications, visit Fair child Semiconductor’s online pac kaging area:
http://www.fairchildsemi.com/packing_dwg/PKG-MA03C_JCET.pdf.
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SOT-89
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 10
Physical Dimensions
Figure 21. 3-LEAD, SOT-23, FLAT LEAD, LOW PROFILE (ACTIVE)
Package drawings are provided as a service to customers considering Fairchild components. Drawings may c hange in any manner
without notic e. Please note the revision and/or date on the drawing and contact a Fairchild Sem iconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the
warranty therein, which covers Fairchild produ cts.
Always visit Fairchild Semiconduct or’s online packaging are a for the most recent package drawings :
http://www.fairchildsemi.com/dwg/MA/MA03E.pdf.
For current tape an d reel specifications, visit Fair child Semiconductor’s online pac kaging area:
http://www.fairchildsemi.com/packing_dwg/PKG-MA03E.pdf.
SOT-23F
LM431SA / LM431SB / LM431SC — Programmable Shunt Regulator
© 2004 Fairchild Semiconductor Corporation www.fairchildsemi.com
LM431SA / LM431SB / LM431SC Rev. 1.3.2 11
Physical Dimensions
Figure 22. 3-LEAD, SOT-23, JEDEC TO-236, LOW PROFILE (ACTIVE)
Package drawings are provided as a service to customers considering Fairchild components. Drawings may c hange in any manner
without notic e. Please note the revision and/or date on the drawing and contact a Fairchild Sem iconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the
warranty therein, which covers Fairchild produ cts.
Always visit Fairchild Semiconduct or’s online packaging are a for the most recent package drawings :
http://www.fairchildsemi.com/dwg/MA/MA03D.pdf.
For current tape an d reel specifications, visit Fair child Semiconductor’s online pac kaging area:
http://www.fairchildsemi.com/packing_dwg/PKG-MA03D_JCET.pdf.
LAND PATTERN
RECOMMENDATION
NOTES: UNLESS OTHERWISE SPECIFIED
A) REFERENCE JEDEC REGISTRATION
TO-236, VARIATION AB, ISSUE H.
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS ARE INCLUSIVE OF BURRS,
MOLD FLASH AND TIE BAR EXTRUSIONS.
D) DIMENSIONING AND TOLERANCING PER
ASME Y14.5M - 1994.
E) DRAWING FILE NAME: MA03DREV10
3
12
SEE DETAIL A
SEATING
PLANE
SCALE: 2X
GAGE PLANE
(0.55)
(0.93)
1.20 MAX
C
0.10
0.00
0.10 C
2.40±0.30
2.92±0.20
1.30+0.20
-0.15
0.60
0.37
0.20AB
1.90
0.95
(0.29)
0.95
1.40
2.20
1.00
1.90
0.25
0.23
0.08
0.20 MIN
SOT-23
© Fairchild Semiconductor Corporation www.fairchildsemi.com
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Definition of Terms
Datasheet Identification
Product Status
Definition
Advance
Information
Formative
/
In Design
Datasheet contains the design specifications for product development. Specifications may change
in any manner without notice.
Preliminary First Production
Datasheet contains preliminary data; supplementary data will be published at a later date. Fairchild
Semiconductor reserves the right to make changes at any time without notice to improve design.
No Identification Needed
Full Production
Datasheet contains final specifications. Fairchild Semiconductor reserves the right to make
changes at any time without notice to improve the design.
Obsolete
Not In Production
Datasheet contains specifications on a product that is discontinued by Fairchild Semiconductor.
The datasheet is for reference information only.
Rev. I65
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