LT431
1 Rev 4.3
Block Diagram & Symbol
Absolute Maximum Ratings
(at TA=25°C)
Characteristics Symbol Rating Unit
Cathode Voltage VKA 40 V
Continuous Cathode Current IKA 250 mA
Reference Input Current IREF 10 mA
Junction Temperature TJ 160 °C
Storage Temperature TSTG -40~150 °C
Power Dissipation (Note1) TO-92 PD 0.68 W
SOT-23 0.25 W
Note1 : Ratings apply to ambient temperature at 25°C
ADJUSTABLE PRECISION SHUNT REGULATOR
FEATURES
• Precision reference voltage :
LT431O : 2.495V±0.4%
LT431N : 2.495V±1.0%
• Adjustable output voltage is VREF to 36V
• Sink current capability is 200mA
• Low dynamic output impedance is 0.2Ω (typ.)
• Minimum Cathode current for regulation is 0.2mA
(typ.)
• Plastic material has UL flammability classification
94V-0
GENERAL DESCRIPTION
The LT431 is a low voltage three terminal
adjustable shunt regulator with a guaranteed
thermal stability over applicable temperature
ranges. The output voltage can be set to any
value between 2.495V (VREF) to 36V with two
external resistors (see application circuit). The
high precise Reference voltage tolerance is
±0.4% and ±1.0% by LT431. This device has a
typical output impedance of 0.2Ω. Active output
circuitry provides a very sharp turn on
characteristic, making this device excel lent
replacement for Zener diodes in many
applications.
LT431
2 Rev 4.3
Recommended Operating Conditions
Characteristics Symbol Min Max Unit
Cathode Voltage VKA V
REF 36 V
Cathode Current IKA 0.5 200 mA
Operating Temperature
(Operating free-air temperature) TA -20 85 °C
Electrical Characteristics
(TA=25°C, unless otherwise specified)
Characteristics Symbol Conditions Min Typ Max Unit
Reference Voltage VREF VKA = VREF,
I KA = 10mA (Fig.1)
0.4 % 2.485 2.495 2.505
V
1.0 % 2.470 2.520
Deviation of Reference Input
Voltage over full temperature
range
VREF(DEV)
VKA = VREF, IKA = 10mA,
TA = -20~85°C (Fig.1) 6.0 20 mV
Reference Input Current IREF R1 = 10KΩ,R2 = ∞ IKA= 10mA
(Fig.2) 1.5 3.5 uA
Deviation of Reference Input
Current over Temperature IREF(DEV)
R1 = 10KΩ,R2 = ∞ IKA = 10mA
TA = -20~85°C (Fig.2) 0.4 1.2 uA
Ratio of the Change in Reference VKA
= 10V ~VREF - -1.2 -2.0
Voltage to the Change in Cathode
Voltage
ΔVREF
ΔVKA
IKA = 10mA
(Fig.2)
VKA = 10V ~VREF -1.2 -2.0
mV/V
VKA= 36V ~10V -1 -2.0
Minimum Cathode Current for
Regulation IKA(min) V
KA = VREF (Fig.1) 0.2 0.5 mA
Off-state Cathode Current IKA(OFF) V
KA = 36V, VREF = 0V (Fig.3) 0.1 1 uA
Dynamic Output Impedance ZKA V KA = VREF
Frequency ≤ 1KHz (Fig.1) 0.2 0.5 Ω
LT431
3 Rev 4.3
Application Circuit
Fig1: VKA=VREF Fig2: VKA>VREF
Fig3: Off state current
LT431
4 Rev 4.3
Typical Characteristics
LT431
5 Rev 4.3
Typical Characteristics (Continued)
(1) Small Signal Voltage Amplification Vs Frequency
(2) Reference Impedance VS Frequency
LT431
6 Rev 4.3
Typical Characteristics (Continued)
(3) Pulse Response
(4) Stability boundary conditions
LT431
7 Rev 4.3
Ordering Information
Product Number Output Voltage
Tolerance Package Lead Free Packing
LT431OHPA 0.4 % TO-92 Green Taping & Reel
LT431NHPA 1.0 % TO-92 Green Taping & Reel
LT431OCAPA 0.4 % SOT-23 Green Taping & Reel
LT431NCAPA 1.0 % SOT-23 Green Taping & Reel
LT431OCRPA 0.4 % SOT-23R Green Taping & Reel
LT431NCRPA 1.0 % SOT-23R Green Taping & Reel
Pin Assignment
Marking Information
LT431 X X X X
Reference Voltage Package Lead Free Packing
Tolerance
O : +/- 0.4%
N : +/- 1.0%
H : TO-92
CA : SOT-23
CR : SOT-23R
P : Green A : Tape & Reel
(
1
)
TO-92
(
2
)
SOT-23
(
3
)
SOT-23R
(Top View) (Top View) (Top View)
CATHODE
ANODE
REF CATHODE
ANODE
REF
3
2
1 REF
ANODE
CATHODE
3
2
1
1) YM = Date Code,
Y: Year, M: Month
2) 431xxx = Product Number
LT431OHPA: 431OHP
LT431NHPA: 431NHP
(
1
)
TO-92
(
2
)
SOT-23 & SOT-23
R
1) YM = Date Code,
Y: Year, M: Month
2) xxx = Product Number
LT431OCAPA: OCA
LT431NCAPA: NCA
LT431OCRPA: OCR
LT431NCRPA: NCR
LT YM
431XXX XXX Y M
LT431
8 Rev 4.3
Mechanical Information
(1) Package type: TO-92
Unit: mm
DIM. MIN. MAX.
A 4.30 4.70
B 4.30 4.70
D 0.38 0.55
E 1.10 1.40
F 3.30 3.70
G 2.44 2.64
H 0.36 0.51
I 1.27 TYP.
J 13.00 14.00
K 3.50 4.50
L 2.20 2.80
LT431
9 Rev 4.3
Mechanical Information (Continued)
(1) Package type: SOT-23 & SOT-23R
Unit: mm
DIM. MIN. MAX.
A 0.89 1.15
B 0.3. 0.51
C 0.08 0.18
D 2.75 3.04
E 1.2 1.4
F 0.95 TYP.
G 1.70 2.10
H 2.10 2.75
I 0.0 0.1
L 0.55 Typ.
L1 0.30 0.50
LT431
10 Rev 4.3
Important Notice and Disclaim er
LSC reserves the right to make changes to this document and its products and
specifications at any time without notice. Customers should obtain and confirm the latest
product information and specifications before final design, purchase or use.
LSC makes no warranty, representation or guarantee regarding the suitability of its products
for any particular purpose, nor does LSC assume any liability for application assistance or
customer product design. LSC does not warrant or accept any liability with products which
are purchased or used for any unintended or unauthorized application.
No license is granted by implication or otherwise under any intellectual property rights of
LSC.
LSC products are not authorized for use as critical components in life support devices or
systems without express written approval of LSC.
