www.fairchildsemi.com
LM431A/LM431B/LM431C
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
Description
The LM431A/LM431B/LM431C 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.
TO-92
1
1. Ref 2. Anode 3. Cathode
8-DIP
8-SOP
1
1
1.Cathode 2.3.4.5.7.NC
6.Anode 8.Ref
1.Cathode 2.3.6.7.Anode
4.5.NC 8.Ref
Internal Block Diagram
REFERENCE
CATHODE
2.5 Vref
ANODE
CATHODE (K)
REFERENCE (R)
ANODE (A)
Rev. 1.0.7
©2003 Fairchild Semiconductor Corporation
LM431A/LM431B/LM431C
Absolute Maximum Ratings
(Operating temperature range applies unless otherwise specified.)
Parameter
Cathode Voltage
Cathode Current Range (Continuous)
Reference Input Current Range
Power Dissipation
M, Z Suffix Package
N Suffix Package
Operating Temperature Range
LM431xC
LM431xI
Junction Temperature
Storage Temperature Range
T
OPR
T
J
T
STG
-25 ~ +85
-40 ~ +85
150
-65 ~ +150
°C
°C
°C
°C
Symbol
V
KA
I
KA
I
REF
P
D
Value
37
-100 ~ +150
-0.05 ~ +10
770
1000
Unit
V
mA
mA
mW
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
LM431A/LM431B/LM431C
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 Cur-
rent for
Regulation
Off - Stage
Cathode
Current
Dynamic
Impedance
Symbol
V
REF
Conditions
V
KA
= V
REF
, I
KA
=10mA
LM431A
LM431B
LM431C
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
-
-1.0
-2.7
-
-1.0
-2.7
-
-1.0
-2.7
mV/V
∆
V
REF
/
∆
V
KA
I
KA
=10mA
∆
V
KA
=36V-
10V
-
-0.5
-2.0
-
-0.5
-2.0
-
-0.5
-2.0
I
REF
I
KA
=10mA,
R
1
=10kΩ,R
2
=∞
-
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
Z
KA
-
0.15
0.5
-
0.15
0.5
-
0.15
0.5
Ω
Note1
• LM431
X
C : T
MIN
= -25
°
C, T
MAX
= +85
°
C
• LM431
X
I : T
MIN
= -40
°
C, T
MAX
= +85
°
C
3
LM431A/LM431B/LM431C
Test Circuits
LM431A/B/C
LM431A/B/C
Figure 1. Test Circuit for V
KA
=V
REF
Figure 2. Test Circuit for V
KA
≥V
REF
LM431A/B/C
Figure 3. Test Circuit for l
KA(OFF)
4
LM431A/LM431B/LM431C
Typical Performance Characteristics
Figure 4.
Cathode Current vs. Cathode Voltage
Figure 5.
Cathode Current vs. Cathode Voltage
Figure 6.
Change In Reference Input Voltage vs.
Cathode Voltage
Figure7. Dynamic Impedance Frequency
Figure 8. Small Signal Voltage Amplification vs. Frequency
Figure 9.
Pulse Response
5
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