July 2006
LM431SA/LM431SB/LM431SC
Programmable Shunt Regulator
Features
Programmable Output Voltage to 36 Volts
Low Dynamic Output Impedance 0.20 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 Turn-on Response
•
•
•
•
tm
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 V
REF
(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 characteristic, making these
devices excellent replacement for Zener Diodes in many
applications.
SOT-89
1
1. Ref 2. Anode 3. Cathode
SOT-23F
3
1
2
1. Cathode 2. Ref 3. Anode
Internal Block Diagram
+
-
Rev. 1.0.5
©2006 Fairchild Semiconductor Corporation
LM431SA/LM431SB/LM431SC
Absolute Maximum Ratings
(Operating temperature range applies unless otherwise specified.)
Parameter
Cathode Voltage
Cathode current Range (Continuous)
Reference Input Current Range
Thermal Resistance Junction-Air (Note1,2)
MF Suffix Package
ML Suffix Package
Power Dissipation (Note3,4)
MF Suffix Package
ML Suffix Package
Junction Temperature
Operating Temperature Range
Storage Temperature Range
Note:
1. Thermal resistance test board
Symbol
V
KA
I
KA
I
REF
R
θJA
Value
37
-100 ~ +150
-0.05 ~ +10
350
220
350
560
150
-25 ~ +85
-65 ~ +150
Unit
V
mA
mA
°C/W
P
D
T
J
T
OPR
T
STG
mW
°C
°C
°C
Size: 76.2mm * 114.3mm * 1.6mm (1S0P)
JEDEC Standard: JESD51-3, JESD51-7
2. Assume no ambient airflow.
3. T
JMAX
= 150
°
C
, Ratings apply to ambient temperature at 25
°
C
4. Power dissipation calculation: P
D
= (T
J
- T
A
)/
R
θJA
Recommended Operating Conditions
Parameter
Cathode Voltage
Cathode Current
Symbol
V
KA
I
KA
Min.
V
REF
1.0
Typ.
-
-
Max.
36
100
Unit
V
mA
2
LM431SA/LM431SB/LM431SC
Electrical Characteristics
(T
A
= +25°C, unless otherwise specified)
Parameter
Reference
Input Voltage
Deviation of
Reference
Input Voltage
Over-
Temperature
Ratio of
Change in
Reference
Input Voltage
to the Change
in Cathode
Voltage
Reference
Input Current
Deviation of
Reference
Input Current
Over Full
Temperature
Range
Minimum
Cathode
Current for
Regulation
Off -Stage
Cathode
Current
Dynamic
Impedance
Symbol
V
REF
Conditions
V
KA
=V
REF
, I
KA
=10mA
LM431SA
LM431SB
LM431SC
Min. Typ. Max. Min. Typ. Max. Min. Typ. Max.
2.450 2.500 2.550 2.470 2.495 2.520 2.482 2.495 2.508
Unit
V
∆
V
REF
/
∆
T
V
KA
=V
REF
, I
KA
=10mA
T
MIN
≤T
A
≤T
MAX
-
4.5
17
-
4.5
17
-
4.5
17
mV
∆
V
KA
=10V-
∆
V
REF
/
∆
V
KA
I
KA
=10mA
V
REF
-
-1.0
-2.7
-
-1.0
-2.7
-
-1.0
-2.7
mV/V
∆
V
KA
=36V-
10V
I
REF
I
KA
=10mA,
R
1
=10KΩ,R
2
=∞
-
-0.5
-2.0
-
-0.5
-2.0
-
-0.5
-2.0
-
1.5
4
-
1.5
4
-
1.5
4
µ
A
I
KA
=10mA,
R
1
=10KΩ,R
2
=∞
∆
I
REF
/
∆
T
T
A
=Full Range
-
0.4
1.2
-
0.4
1.2
-
0.4
1.2
µ
A
I
KA(MIN)
V
KA
=V
REF
-
0.45
1.0
-
0.45
1.0
-
0.45
1.0
mA
I
KA(OFF)
V
KA
=36V, V
REF
=0
V
KA
=V
REF
,
I
KA
=1 to 100mA ,f
≥1.0kHz
-
0.05
1.0
-
0.05
1.0
-
0.05
1.0
µ
A
Ω
Z
KA
-
0.15
0.5
-
0.15
0.5
-
0.15
0.5
Note1
T
MIN
= -25°C, T
MAX
= +85°C
3
LM431SA/LM431SB/LM431SC
Test Circuits
LM431S
LM431S
Figure 1. Test Circuit for V
KA
=V
REF
Figure 2. Test Circuit for V
KA
≥V
REF
LM431S
Figure 3. Test Circuit for l
KA(OFF)
4
LM431SA/LM431SB/LM431SC
Typical Performance Characteristics
800
150
V
KA
= V
REF
T
A
= 25 C
o
V
KA
= V
REF
T
A
= 25 C
o
600
100
I
KA
, CATHODE CURRENT (uA)
I
K
, Cathode Current (mA)
400
50
I
KA(MIN)
0
200
-50
0
-100
-2
-1
0
1
2
3
V
KA
, Cathode Voltage (V)
-200
-1
0
1
V
KA
, CATHODE VOLTAGE (V)
2
3
Figure 4. Cathode Current vs. Cathode Voltage
Figure 5. Cathode Current vs. Cathode Voltage
0.100
3.5
3.0
I
off
, Off-State Cathode Current (uA)
0.075
I
ref
, Reference Input Current (uA)
-25
0
25
50
75
o
2.5
2.0
0.050
1.5
0.025
1.0
0.5
0.000
-50
100
125
0.0
-50
-25
0
25
50
75
o
100
125
T
A
, Ambient Temperature ( C)
T
A
, Ambient Temperature ( C)
Figure 6. OFF-State Cathode Current vs.
Ambient Temperature
6
60
T
A
= 25 C
I
KA
= 10mA
o
Figure7. Reference Input Current vs.
Ambient Temperature
T
A
=25 C
o
50
5
INPUT
40
Open Loop Voltage Gain (dB)
4
Voltage Swing (V)
30
3
OUTPUT
20
2
10
1
0
-10
1k
10k
100k
Frequency (Hz)
0
1M
10M
0
4
8
Time (us)
12
16
20
Figure 8. Small Signal Voltage Amplification vs. Frequency
Figure 9. Pulse Response
5
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