ETC2 L431LM5B 1.24v low-voltage adjustable precision shunt regulator Datasheet

1.24V Low-Voltage Adjustable
Precision Shunt Regulator
NIKO-SEM
L431L
GENERAL DESCRIPTION
FEATURES
The L431L is a three-terminal adjustable shunt
regulator utilizing an accurate 1.24V band gap
reference. The output voltage can be set to any
value between 1.24V (VREF) to 18V with two
external resistors as shown in the typical
application circuit. The device exhibit a wide
operating current range of 0.2 to 100 mA with a
typical dynamic impedance of 0.25Ω. Active
output circuitry provides a very sharp turn-on
characteristic, making the L431L excellent replacements for low-voltage zener diodes in
many applications, including on-board regulation and adjustable power supplies.
When used with an opto-coupler, the L431L is
ideal voltage reference in isolated feedback
circuits for 3.3V switching-mode power supplies.
The L431L shunt regulator is available in two
voltage tolerances (0.5% & 1.0%) and three
package options (TO-92, SOT-23-3 and SO-8).
z Internal amplifier with 100 mA capability
z Programmable output voltage to 18V
z 0.25Ω typical output impedance
z Pin to pin compatible with TLV431A,
TS431, SC431L & AS432
z Trimmed bandgap design 0.5% & 1.0%
with three package options
z Low output noise
APPLICATIONS
z Linear regulator controller
z Precision voltage reference
z Switching power supplies
z Battery operating equipment
z Instrumentation
z PCs, Computer disk drives
SYMBOL & BLOCK DIAGRAM
Cathode (K)
Reference
(R)
+
Cathod
(K)
-
Reference (R)
1.24 Vref
Anode (A)
Anode (A)
SYMBOL
FUNCTIONAL BLOCK DIAGRAM
1
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
ABSOLUTE MAXIMUM RATINGS
PARAMETER
VALUE
Cathode-Anode Reverse Breakdown Voltage - VKA
Anode-Cathode Forward Current - IAK
Operating Cathode Current - IKA
Reference Input Current - IREF
Storage Temperature Range - TSTG
Junction Temperature - TJ
Lead Temperature (Soldering, 10 Seconds) - TL
Continuous Power at 25 °C - PD
TO-92
SOIC-8
SOT-23
RECOMMENDED CONDITIONS
Parameter
Cathode Voltage (VKA)
Cathode Current (IK)
Rating
VREF to 18V
10 mA
20V
1A
100 mA
1 mA
-65 to +150 °C
150 °C
300 °C
700 mW
650 mW
200 mW
TYPICAL THERMAL RESISTANCES
Package
TO-92
SOIC-8
SOT-23
Typ. De-rating
θJA
θJC
160 °C/W 80 °C/W
6.3 mW/°C
175 °C/W 45 °C/W
5.7 mW/°C
575 °C/W 150 °C/W
1.7 mW/°C
ELECTRICAL SPECIFICATIONS
(Ambient temperature must be derated base on power dissipation and package thermal characteristics. The conditions are: VKA = VREF and
IK = 10 mA unless otherwise stated)
PARAMETER
Output Voltage - VREF
TEST
TYP MAX UNITS CIRCUIT
TA = 25 °C, L432 (0.5%) 1.234 1.240 1.246 V
1
TA = 25 °C, L432 (1%) 1.228 1.240 1.252
mV
VKA = VREF to 15V
28
50
2
mV
IK = 1 to 100 mA
3.9
6
1
mV
0 < TJ < 105 °C
5
12
1
µA
2.3
6
1
TEST CONDITIONS
Line Regulation - ∆VREF
Load Regulation - ∆VREF
Temperature Deviation - ∆VREF
Reference Input Current - IREF
Reference Input Current
0 < TJ < 105 °C
Temperature Coefficient - ∆IREF
Minimum Cathode Current
for Regulation - IK(MIN)
Off State Leakage - IK(MIN)
VREF = 0V, VKA = 15V
Dynamic impedance
VKA = Vref, f ≦ 1kHz
IK = 0.1 mA to 100 mA
2
MIN
0.14
0.6
µA
1
0.2
1
mA
1
40
0.25
500
0.4
nA
Ω
3
1
APR-25-2002
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
NIKO-SEM
L431L
TEST CIRCUITS
VIN
VKA
I REF
IK
VIN
VKA
R1
I REF
IK
VIN
VKA
I K (OFF)
V REF
R2
- TEST CIRCUIT 1 (VKA = VREF)
- TEST CIRCUIT 2 (VKA > VREF)
- TEST CIRCUIT 3 (OFF STATE CURRENT)
Applications Information – Stability
Selection of load capacitance when using
L431L as a shunt regulator
When the L431L is used as a shunt regulator,
two options for selection of CL are
recommended for optimal stability:
1. No load capacitance across the device,
decouple at the load.
2. Large capacitance across the device,
optional decoupling at the load.
The reason for this is that L431L exhibits
instability with capacitances in the range of
1nF to 1uf (approx.) at light cathode currents
(up to 3mA typical). The device is less stable
the lower the cathode voltage has been set for.
Therefore while the device will be perfectly
stable operating at a cathode current of 10mA
with a 0.1uF capacitor across it, it will oscillate
transiently during start-up as the cathode
current passes through the instability region.
Selecting a very low
3
(or preferably, no)capacitance, or alternatively a high capacitance (such as 10uF)
will avoid this issue altogether. Since the
user will probably wish to have local
decoupling at the load anyway, the most
cost effective method is to use no
capacitance at all directly across the
device. PCB trace/via resistance and
inductance prevent the local load decoupling from causing the oscillation during
the transient start-up phase. Note : if the
L431L is located right at the load, so the
load decoupling capacitor is directly across
it, then this capacitor will have to be
≦ 100pF or ≧ 1uF.
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
Small-Signal Gain and Phase Shift
VS. Frequency
Test Circuit for Small Signal Gain and Phase
OUT
15K
Iz
3
1
1
1
10uF
232
L431L
2
8.25K
2
2
GND
Test Circuit for Stability
Stability Boundary Condition For Shunt Regulation
VS. Cathode Current and Load Capacitance
R
3
Iz
R1
1
1
2
2
Cathode Current
VS. Cathode Voltage
CL
L431L
R2
Cathode Current
VS. Cathode Voltage
4
APR-25-2002
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
NIKO-SEM
Reference Voltage
VS. Junction Temperature
L431L
Ω
Reference Impedance
VS. Frequency
Ratio of Delta Reference Voltage to Delta Cathode Voltage
VS. Junction Temperature
Reference Input Current
VS. Junction Temperature
ΔVref /ΔVz (-mV/V)
ΔVz = 16V to Vref
∞
5
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
Off-State Cathode Current
VS. Junction Temperature
Reference Impedance
rz (Ω)
VS. Junction Temperature
PIN CONFIGURATIONS
6
APR-25-2002
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
NIKO-SEM
L431L
DEVICE SELECTION GUIDE
Device
L431LNB
L431LM3B
L431LVB
L431LM5B
Package
TO-92
SOT-23-3
SOIC-8
SOT-23-5
Marking
L431LN
1LM3
L431LV
Tolerance
1%
1%
1%
1LM5
1%
APPLICATION CIRCUIT
P01N02LM or P3055L
Niko
Vin
+ D
Vout
S
Cin
G
R1
5V or 12V
+
1K
Cout
K
+
R
A L431L
Niko
10uF
Vout = (1 +
7
R1
R2
R2
) Vref
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
TO-92 MECHANICAL DATA
Dimension
mm
Min.
Typ.
Dimension
Max.
mm
Min.
Typ.
Max.
2.540
2.667
A
4.445
5.207
H
2.413
B
4.318
5.334
I
0.356
C
12.7
15.5
J
D
0.356
0.533
K
E
1.143
1.397
L
F
3.175
4.191
M
G
0.762
1.270
N
1.27
8
0.533
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
SOT-23 (M3) MECHANICAL DATA
Dimension
mm
Min.
A
Typ.
Dimension
Max.
0.95
Min.
Typ.
Max.
H
0.10
0.15
0.25
0.37
B
2.60
2.80
3.00
I
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
0.5
N
0.4
9
mm
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
SOIC-8 (D) MECHANICAL DATA
Dimension
mm
Min.
Typ.
Dimension
Max.
mm
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
D
0.35
0.48
K
E
1.27
F
G
0.1
0.22
0°
8°
L
1.65
M
0.25
N
10
APR-25-2002
NIKO-SEM
1.24V Low-Voltage Adjustable
Precision Shunt Regulator
L431L
SOT-23 (M5) MECHANICAL DATA
Dimension
mm
Dimension
mm
Min.
Typ.
Max.
A
1.0
1.10
1.30
e
A1
0.00
0.10
H
2.60
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
E
1.40
1.60
1.80
11
Min.
Typ.
Max.
1.90(TYP)
2.80
3.00
APR-25-2002
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