LR8
High Input Voltage,
Adjustable 3-Terminal Linear Regulator
Features
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13.2 - 450V input voltage range
Adjustable 1.20 - 440V output regulation
5% output voltage tolerance
Output current limiting
10µA typical ADJ current
Internal junction temperature limiting
General Description
The Supertex LR8 is a high voltage, low output current,
adjustable linear regulator. It has a wide operating input voltage
range of 13.2 - 450V. The output voltage can be adjusted from
1.20 - 440V provided that the input voltage is at least 12V
greater than the output voltage. The output voltage can be
adjusted by means of two external resistors R1 and R2 as
shown in the typical application circuits. The LR8 regulates the
voltage difference between VOUT and ADJ pins to a nominal
value of 1.20V. The 1.20V is amplified by the external resistor
ratio R1 and R2. An internal constant bias current of typically
10µA is connected to the ADJ pin. This increases V
OUT
by a
constant voltage of 10µA times R2.
The LR8 has current limiting and temperature limiting. The
output current limit is typically 20mA and the minimum
temperature limit is 125°C. An output short circuit current will
therefore be limited to 20mA. When the junction temperature
reaches its temperature limit, the output current and/or output
voltage will decrease to keep the junction temperature from
exceeding its temperature limit. For SMPS start-up circuit
applications, the LR8 turns off when an external voltage
greater than the output voltage of the LR8 is applied to VOUT
of the LR8. To maintain stability, a bypass capacitor of 1.0µF
or larger and a minimum DC output current of 500µA are
required.
The device is available in TO-243AA (SOT-89), TO-252 (D-
PAK), and TO-92 packages.
Applications
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Off-line SMPS startup circuits
Adjustable high voltage constant current source
Industrial controls
Motor controls
Battery chargers
Power supplies
Typical Application Circuit
*
VIN
VIN VOUT
ADJ
V
OUT
LR8
C1
R2
R1
C2
R
LOAD
*Required for conditions where V
IN
is less than V
OUT
.
LR8
Ordering Information
Device
LR8
-G indicates package is RoHS compliant (‘Green’)
Package Options
TO-252 (D-PAK)
LR8K4-G
TO-92
LR8N3-G
TO-243AA (SOT-89)
LR8N8-G
Pin Configurations
VOUT
VIN
ADJ
VIN
ADJ
VOUT
Absolute Maximum Ratings
Parameter
V
IN
input voltage (voltages ref to ADJ)
Output voltage range
Operating ambient temperature range
Operating junction temperature range
Storage temperature range
Value
-0.5V to +480V
-0.5V to +470V
-40°C to +85°C
-40°C to +125°C
-65°C to +150°C
TO-252 (K4)
VOUT
TO-92 (N3)
ADJ
VOUT
VIN
TO-243AA (SOT-89) (N8)
Product Marking
YYWW
LR8
LLLLLLL
YY = Year Sealed
WW = Week Sealed
L = Lot Number
= “Green” Packaging
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent
damage to the device. These are stress ratings only, and functional operation of the
device at these or any other conditions beyond those indicated in the operational sections
of the specifications is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
TO-252 (K4)
LR
8
YWLL
Y = Last Digit of Year Sealed
W = Code for Week Sealed
L = Lot Number
= “Green” Packaging
TO-92 (N3)
LR8W
W = Code for Week Sealed
= “Green” Packaging
TO-243AA (SOT-89) (N8)
Electrical Characteristics
Sym
V
IN
- V
OUT
V
OUT
V
OUT
ΔV
OUT
ΔV
OUT
ΔV
OUT
Parameter
(Test conditions unless otherwise specified: -40°C < T
A
< 85°C.)
Min
12
1.14
375
-
-
-1
Typ
-
1.20
400
0.003
1.4
-
Max
450
1.26
425
0.01
3.0
+1
Units Conditions
V
V
V
%/V
%
%
---
13.2V < V
IN
< 400V,
R1 = 2.4KΩ, R2 = 0
R1 = 2.4KΩ, R2 = 782KΩ
17V < V
IN
< 400V, V
OUT
= 5V,
I
OUT
= 0.5mA
V
IN
= 17V, V
OUT
= 5V,
0.5mA <I
OUT
< 10mA
V
IN
= 17V, V
OUT
= 5V, I
OUT
= 10mA,
-40°C < T
A
< 85°C
Input to output voltage difference
Overall output voltage regulation
Overall output voltage regulation
Line regulation
Load regulation
Temperature regulation
2
LR8
Electrical Characteristics
(cont.)
Sym
I
OUT
I
OUT
I
OUT
I
ADJ
C2
DV
OUT
/DV
IN
T
LIMIT
Parameter
Output current limit
Output current limit
Minimum output current
Adjust output current
Minimum output load capacitance
Ripple rejection ratio
Junction temperature limit
(Test conditions unless otherwise specified: -40°C < T
A
< 85°C.)
Min
10
-
-
5.0
1.0
50
125
Typ
-
-
0.3
10
-
60
-
Max
30
0.5
0.5
15
-
-
-
Units Conditions
mA
mA
mA
µA
µF
dB
°C
T
J
< 85°C, V
IN
- V
OUT
= 12V
T
J
> 125°C, V
IN
- V
OUT
= 450V
Includes R1 and load current
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120Hz, V
OUT
= 5V
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Thermal Characteristics
Package
TO-92
TO-243AA
TO-252
Power Dissipation
@ T
A
= 25°C
°C/W
θ
jc
°C/W
θ
ja
0.74W
1.6W
2.5W
125
15
6.25
170
78
†
50
†
Note:
† Mounted on FR4 board, 25mm x 25mm x 1.57mm.
Functional Block Diagram
VIN
Pass
Element
LR8
VOUT
Overtemp &
Overcurrent
1.2V
10µA
ADJ
3
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