Page 1
NIKO-SEM
2.5V Low-Voltage Adjustable
Precision Shunt Regulator
GENERAL DESCRIPTION
FEATURES
L431
The L431 is a three-terminal adjustable shunt
regulator utilizing an accurate 2.5V band-gap
reference. The output voltage can be set to any
value between 2.5V (V
) to 29V with two
REF
external resistors as shown in the typical
application circuit. The device exhibit a wide
operating current range of 0.4 to 100 mA with a
typical dynamic impedance of 0.25Ω. The cha-
racteristics of these reference make it excellent replacements for zener diodes in many
applications such as digital voltmeters, power
supplies, and op amp circuitry. The 2.5V volt
reference makes it convenient to obtain a
stable reference from 5.0V logic supplies.
The L431 shunt regulator is available in three
voltage tolerances (0.5%, 1.0% and 2%) and
three package options (TO-92, SOT-23-3,
SOT-23-5 and SOIC-8).
SYMBOL & BLOCK DIAGRAM
z Internal amplifier with 70 mA capability
z Programmable output voltage to 29V
z 0.25Ωtypical output impedance
z Pin to pin compatible with TL431, LM431
, SC431 & AS431
z Trimmed band-gap design 0.5%, 1.0%
and 2% with three package options
z Low cost solution
APPLICATIONS
z Linear regulator controller
z Precision voltage reference
z Switching power supplies
z Battery operating equipment
z Instrumentation
z PCs, Computer disk drives
Reference (R)
Cathode (K)
Anode (A)
SYMBOL
Reference
(R) (K)
+
-
2.5 Vref
Anode (A)
FUNCTIONAL BLOCK DIAGRAM
Cathod
1
JAN-08-Y02
Page 2
NIKO-SEM
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
ABSOLUTE MAXIMUM RATINGS
PARAMETER VALUE
Cathode-Anode Reverse Breakdown Voltage - VKA 30V
Anode-Cathode Forward Current - IAK 70 mA
Reference Input Current - I
Storage Temperature Range - T
Junction Temperature - TJ 150 °C
Lead Temperature (Soldering, 10 Seconds) - TL 300 °C
Continuous Power at 25 °C - P
TO-92
SOIC-8
SOT-23
10 mA
REF
-65 to +150 °C
STG
D
700 mW
650 mW
200 mW
RECOMMENDED CONDITIONS TYPICAL THERMAL RESISTANCES
Parameter Rating Package
Cathode Voltage (VKA) V
to 29V TO-92 160 °C/W 80 °C/W 6.3 mW/°C
REF
θJA θJC
Cathode Current (IK) 10 mA SOIC-8 175 °C/W 45 °C/W 5.7 mW/°C
SOT-23 575 °C/W 150 °C/W 1.7 mW/°C
Typ. Derating
ELECTRICAL SPECIFICATIONS
(Ambient temperature must be derated base on power dissipation and package thermal characteristics. The conditions are: VKA = V
= 10 mA unless otherwise stated)
I
K
PARAMETER TEST CONDITIONS MIN TYP MAX
Reference Voltage
TA = 25 °C, L431 (0.5%) 2.482 2.495 2.507
TA = 25 °C, L431 (1%) 2.470 2.495 2.520
UNITS
V
TA = 25 °C, L431 (2%) 2.445 2.495 2.550
∆V
Cathode Voltage
with Temp. 0.07 0.2
REF
V
REF
to
REF
to 10V -2.7 -1.0 Ration of Change in V
10V to 30V -2.0 -0.4 0.3
Reference Input Current 0.7 4
I
Temp. Deviation Over Temp. 0.4 1.2
REF
Min. IK for Regulation 0.4 1
Off State Leakage V
Dynamic Output Impedance
= 0V, VKA = 30V 0.04 250
REF
f ≤ 1KHz, IK = 1 to 70 mA
0.25 0.5
mV/°C
mV/V
µA
µA
mA
nA
Ω
and
REF
TEST
CIRCUIT
1
1
2
2
2
1
3
1
2
JAN-08-Y02
Page 3
NIKO-SEM
TEST CIRCUITS
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
V
IN
I
REF
V
I
K
KA
IN
R1
V
REF
R2
- TEST CIRCUIT 1 -
KA
(V
)V
REF
=
- TEST CIRCUIT 2 -
Stability Boundary Condition For Shunt Regulation
VS. Cathode Current and Load Capacitance
I
KA
REF
VV
VV
KA
IN
I
K
I
KA
K (OFF)
- TEST CIRCUIT 3 -
>(V
V
)
REF
(OFF STATE CURRENT)
Test Circuit for Vka > Vref
12
150
Ik
R1
1023 4 56
The areas under the curves represent conditions that may
cause the device to oscillate. For curves B, C and D, R
V
BATT were adjusted to establish the initial VKA and IKA
conditions with C
to determine the ranges of stability.
L = 0. VBATT and CL then were adjusted
1 and
3
1
L431
2 3
R2
10K
CLVBATT
Test Circuit for Vka = Vref
150
12
Ik
1
CL
L431
2 3
JAN-08-Y02
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e
NIKO-SEM
Small-Signal Gain and Phase Shift
VS. Frequency
2.5V Low-Voltage Adjustable
Precision Shunt Regulator
Test Circuit for Small Signal Gain and Phas
15K
L431
OUT
232
Ik
Cathode Current
VS. Cathode Voltage
1
12
10uF
8.25K
2 3
12
L431
GND
Cathode Current
VS. Cathode Voltage
Reference Impedance
VS. Junction Temperature
)
Ω
(
z
r
4
Ratio of Delta Reference Voltage to Delta Cathode Voltage
VS. Junction Temperature
)
V
/
V
m
ΔVz = 3V to 30V
(
z
V
Δ
/
f
e
r
V
Δ
JAN-08-Y02
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NIKO-SEM
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
Off-State Cathode Current
VS. Junction Temperature
∞
Reference Input Current
VS. Junction Temperature
Reference Impedance
VS. Frequency
Reference Voltage
VS. Junction Temperature
Ω
5
JAN-08-Y02
Page 6
NIKO-SEM
PIN CONFIGURATION
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
DEVICE SELECTION GUIDE
Device
Package
Marking
Tolerance
L431NA L431M3A L431VA L431M5A
TO-92 SOT-23-3 SOIC-8 SOT-23-5
L431N 1M3 L431V 1M5A
0.5% 0.5% 0.5% 0.5%
6
JAN-08-Y02
Page 7
A
NIKO-SEM
APPLICATION CIRCUIT
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
5V or 12V
Vin
Cin
+
P01N02LM or P3055L
D S
+
1K
G
K R
10uF
Niko
L431 or L432
Niko
R1
R2
+
Cout
Vout
R1
Vout = (1 + ) Vref
R2
7
JAN-08-Y02
Page 8
NIKO-SEM
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
TO-92 MECHANICAL DATA
Dimension
Min. Typ. Max.
mm mm
Dimension
Min. Typ. Max.
A 4.445 5.207 H 2.413 2.540 2.667
B 4.318 5.334 I 0.356 0.533
C 12.7 15.5 J
D 0.356 0.533 K
E 1.143 1.27 1.397 L
F 3.175 4.191 M
G 0.762 1.270 N
8
JAN-08-Y02
Page 9
NIKO-SEM
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
SOT-23 (M3) MECHANICAL DATA
Dimension
Min. Typ. Max.
mm mm
Dimension
Min. Typ. Max.
A 0.95 H 0.10 0.15 0.25
B 2.60 2.80 3.00 I 0.37
C 1.40 1.60 1.80 J
D 2.70 2.90 3.10 K
E 1.00 1.10 1.30 L
F 0.00 0.10 M
G 0.35 0.4 0.5 N
9
JAN-08-Y02
Page 10
NIKO-SEM
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
SOIC-8 (D) MECHANICAL DATA
Dimension
Min. Typ. Max.
mm mm
Dimension
Min. Typ. Max.
A 4.8 5.0 H 0.4 1.27
B 3.8 4.0 I 0.18 0.25
C 5.8 6.2 J 0.22
D 0.35 0.48 K
E 1.27 L
F 1.65 M
G 0.1 0.25 N
0°
8°
10
JAN-08-Y02
Page 11
NIKO-SEM
2.5V Low-Voltage Adjustable
L431
Precision Shunt Regulator
SOT-23 (M5) MECHANICAL DATA
mm mm
Dimension
Min. Typ. Max.
A 1.0 1.10 1.30 e 1.90(TYP)
A1 0.00 0.10 H 2.60 2.80 3.00
A2 0.70 0.80 0.90 L 0.37
b 0.35 0.40 0.50
C 0.10 0.15 0.25
D 2.70 2.90 3.10
Dimension
Min. Typ. Max.
E 1.40 1.60 1.80
11
JAN-08-Y02
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