LM431 Adjustable Precision Zener Shunt Regulator
September 2, 2010
LM431
Adjustable Precision Zener Shunt Regulator
General Description
The LM431 is a 3-terminal adjustable shunt regulator with
guaranteed temperature stability over the entire temperature
range of operation. The output voltage may be set at any level
greater than 2.5V (V
REF
) up to 36V merely by selecting two
external resistors that act as a voltage divided network. Due
to the sharp turn-on characteristics this device is an excellent
replacement for many zener diode applications.
Features
■
Average temperature coefficient 50 ppm/°C
■
Temperature compensated for operation over the full
temperature range
■
Programmable output voltage
■
Fast turn-on response
■
Low output noise
Connection Diagrams
TO-92: Plastic Package
SOT-23: 3-Lead Small Outline
1005528
1005501
Top View
Top View
SO-8: 8-Pin Surface Mount
1005502
Top view
Note: NC = Not internally connected.
© 2010 National Semiconductor Corporation
10055
www.national.com
LM431
Ordering Information
Package
TO-92
Typical Accuracy Order Number/Package Marking
0.5%
LM431CCZ/
LM431CCZ
LM431CIZ/
LM431CIZ
SO-8
LM431CCM/
431CCM
LM431CCMX/
431CCM
LM431CIM/
431CIM
LM431CIMX/
431CIM
SOT-23
LM431CCM3/
N1B
LM431CCM3X/
N1B
LM431CIM3
N1A
LM431CIM3X
N1A
1%
LM431BCZ/
LM431BCZ
LM431BIZ/
LM431BIZ
LM431BCM/
431BCM
LM431BCMX/
431BCM
LM431BIM/
431BIM
LM431BIMX/
431BIM
LM431BCM3/
N1D
LM431BCM3X/
N1D
LM431BIM3
N1C
LM431BIM3X
N1C
2%
LM431ACZ/
LM431ACZ
LM431AIZ/
LM431AIZ
LM431ACM/
LM431ACM
LM431ACMX/
LM431ACM
LM431AIM/
LM431AIM
LM431AIMX/
LM431AIM
LM431ACM3/
N1F
LM431ACM3X/
N1F
LM431AIM3
N1E
LM431AIM3X
N1E
Temperature
Range
0°C to +70°C
Rails
−40°C to +85°C
Rails
0°C to +70°C
Tape & Reel
M08A
Rails
−40°C to +85°C
Tape &Reel
Rails
0°C to +70°C
Tape & Reel
MF03A
Rails
−40°C to +85°C
Tape &Reel
Z03A
Transport
Media
NSC
Drawing
Symbol and Functional Diagrams
1005599
1005555
www.national.com
2
LM431
DC Test Circuits
1005504
1005505
Note:
V
Z
= V
REF
(1 + R1/R2) + I
REF
• R1
FIGURE 1. Test Circuit for V
Z
= V
REF
FIGURE 2. Test Circuit for V
Z
> V
REF
1005506
FIGURE 3. Test Circuit for Off-State Current
3
www.national.com
LM431
Absolute Maximum Ratings
(Note
1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Storage Temperature Range
Operating Temperature Range
Industrial (LM431xI)
Commercial (LM431xC)
Soldering Information
Infrared or Convection (20 sec.)
Wave Soldering (10 sec.)
Cathode Voltage
Continuous Cathode Current
Reference Voltage
Reference Input Current
Internal Power Dissipation (Note
2,
Note 3)
TO-92 Package
SO-8 Package
SOT-23 Package
−65°C to +150°C
−40°C to +85°C
0°C to +70°C
235°C
260°C (lead temp.)
37V
−10 mA to +150 mA
−0.5V
10 mA
0.78W
0.81W
0.28W
Operating Conditions
Cathode Voltage
Cathode Current
Min
V
REF
1.0 mA
Max
37V
100 mA
LM431 Electrical Characteristics
T
A
= 25°C unless otherwise specified
Symbol
V
REF
Parameter
Reference Voltage
Conditions
V
Z
= V
REF
, I
I
= 10 mA
LM431A
(Figure
1
)
V
Z
= V
REF
, I
I
= 10 mA
LM431B
(Figure
1
)
V
Z
= V
REF
, I
I
= 10 mA
LM431C
(Figure
1
)
V
DEV
Deviation of Reference Input Voltage Over
Temperature (Note
4)
Ratio of the Change in Reference Voltage
to the Change in Cathode Voltage
I
REF
∝I
REF
Reference Input Current
Deviation of Reference Input Current over
Temperature
I
Z(MIN)
I
Z(OFF)
r
Z
Minimum Cathode Current for Regulation
Off-State Current
Dynamic Output Impedance (Note
5)
V
Z
= V
REF
, I
I
= 10 mA,
T
A
= Full Range
(Figure
1
)
I
Z
= 10 mA
(Figure
2
)
V
Z
from V
REF
to 10V
V
Z
from 10V to 36V
−1.4
−1.0
2.0
−2.7
−2.0
4.0
μA
mV/V
8.0
17
mV
2.485
2.500
2.510
V
2.470
2.495
2.520
V
Min
2.440
Typ
2.495
Max
2.550
Units
V
R
1
= 10 kΩ, R
2
=
∞
,
I
I
= 10 mA
(Figure
2
)
R
1
= 10 kΩ, R
2
=
∞
,
I
I
= 10 mA,
T
A
= Full Range
(Figure
2
)
V
Z
= V
REF
(Figure
1
)
V
Z
= 36V, V
REF
= 0V (Figure
3)
V
Z
= V
REF
, LM431A,
Frequency = 0 Hz
(Figure
1
)
V
Z
= V
REF
, LM431B, LM431C
Frequency = 0 Hz
(Figure
1
)
0.4
0.4
0.3
1.2
1.0
1.0
0.75
0.50
μA
mA
μA
Ω
Ω
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating conditions.
Note 2:
T
J Max
= 150°C.
Note 3:
Ratings apply to ambient temperature at 25°C. Above this temperature, derate the TO-92 at 6.2 mW/°C, the SO-8 at 6.5 mW/°C, the SOT-23 at 2.2 mW/
°C.
Note 4:
Deviation of reference input voltage, V
DEV
, is defined as the maximum variation of the reference input voltage over the full temperature range.
www.national.com
4
LM431
1005507
The average temperature coefficient of the reference input voltage, ∝V
REF
, is defined as:
Where:
T
2
− T
1
= full temperature change (0-70°C).
∝V
REF
can be positive or negative depending on whether the slope is positive or negative.
Example: V
DEV
= 8.0 mV, V
REF
= 2495 mV, T
2
− T
1
= 70°C, slope is positive.
Note 5:
The dynamic output impedance, r
Z
, is defined as:
When the device is programmed with two external resistors, R1 and R2, (see
Figure 2
), the dynamic output impedance of the overall circuit, r
Z
, is defined as:
Equivalent Circuit
1005503
5
www.national.com
京公网安备 11010802033920号
EEWORLD
