LR8.pdf

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LR8
LR8
New Product
High Input Voltage
Adjustable 3-Terminal Linear Regulator
Ordering Information
Maximum Input
Voltage
450V
Package Options
TO-92
LR8N3
TO-243AA*
LR8N8
General Description
The Supertex LR8 is a high voltage, low output current, adjust-
able linear regulator. It has a wide operating input voltage range
of 12V to 450V. The output voltage can be adjusted from 1.20V
to 440V provided that the input voltage is at least 10V 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 differ-
ence between V
OUT
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 15mA and the minimum tempera-
ture limit is 125°C. An output short circuit current will therefore be
limited to 15mA. 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 V
OUT
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-92 and TO243AA packages.
*Same as SOT-89. Product supplied on 2000 piece carrier tape reels.
Features
❏
❏
❏
❏
❏
❏
12V to 450V input voltage range
Adjustable 1.20V to 440V output regulation
5% output voltage tolerance
Output current limiting
10µA typical ADJ current
Internal junction temperature limiting
Applications
❏
❏
❏
❏
❏
❏
Off-line SMPS startup circuits
Adjustable high voltage constant current source
Industrial Controls
Motor controls
Battery chargers
Power supplies
Pin Configuration
1
2
3
TAB
Absolute Maximum Ratings
V
IN
Input Voltage
Output Voltage Range
Operating Ambient Temperature Range
Operating Junction Temperature Range
Storage Temperature Range
*All voltages referenced to ADJ.
-0.5V to +480V
-0.5V to +470V
-40°C to +85°C
-40°C to +125°C
-65°C to +150°C
TO-92
TO-243AA
TO-243AA
(SOT-89)
123
TO-92
V
IN
1
1
ADJ
3
3
V
OUT
2
2, TAB
01/05/00
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability
indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to
workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For complete liability information covering this and
other Supertex products, refer to the Supertex 1998 Databook.
1
LR8
Thermal Characteristics
Package
TO-92
TO-243AA
†
Power Dissipation
@ T
A
=25
°
C
0.74W
1.6W
°
C/W
125
15
θ
JC
°
C/W
170
78
†
θ
JA
Mounted on FR4 board, 25mm x 25mm x 1.57mm.
Significant P
D
increase possible on ceramic substrate.
Electrical Characteristics
Test conditions unless otherwise specified:
-40°C < T
A
< 85°C.
Symbol
V
IN
- V
OUT
V
OUT
V
OUT
∆V
OUT
∆V
OUT
∆V
OUT
I
OUT
I
OUT
I
OUT
I
ADJ
C2
Parameter
Input to Output Voltage Difference
Overall Output Voltage Regulation
Overall Output Voltage Regulation
Line Regulation
Load Regulation
Temperature Regulation
Output Current Limit
Output Current Limit
Minimum Output Current
Adjust Output Current
Minimum Output Load Capacitance
5
1
50
125
60
0.3
10
-1
10
Min
12
1.14
375
1.20
400
0.003
1.4
Typ
Max
450
1.26
425
0.01
3.0
+1
20
0.5
0.5
15
Units
V
V
V
%/V
%
%
mA
mA
mA
µA
µF
dB
°C
120Hz, V
OUT
= 5V
12V<V
IN
<400V, R1=2.4KΩ, R2=0
R1=2.4KΩ, R2=782KΩ
15V<V
IN
<400V, V
OUT
=5V, I
OUT
=0.5mA
V
IN
=15V, V
OUT
=5V, 0.5mA<I
OUT
<10mA
V
IN
=15V, V
OUT
=5V, I
OUT
=10mA,
-40°C<T
A
<85°C
T
J
< 85°C, V
IN
- V
OUT
= 10V
T
J
> 125°C, V
IN
- V
OUT
= 450V
Includes R1 and load current
Test Conditions
DV
OUT
/DV
IN
Ripple Rejection Ratio
T
LIMIT
Junction Temperature Limit
Functional Block Diagram
VIN
Series
Pass
Element
VOUT
A
Current &
Temperature
Limiting
ADJ
2
LR8
Typical Application Circuits
*
VOUT=5.0V
R1
6.04KΩ
±1%
R2
18.2KΩ
±1%
VOUT = 1.20V 1+ R2 + IADJ R2
R1
V
IN
=15V to 450V
V
IN
V
ADJ
OUT
LR8
C1
C2
1.0µF
R
LOAD
≤16.5KΩ
Figure 1: High Input Voltage, 5.0V Output Linear Regulator
* Required for conditions where V
IN
is less than V
OUT
.
V
IN
=15V to 450V
VAuxiliary
+
Vout1
-
+
Vcc
PWM IC
Vout2
-
LR8
V
IN
V
OUT
ADJ
Figure 2: SMPS Start-Up Circuit
LR8
+
V
IN
= 15V
to 450V
-
V
IN
V
OUT
ADJ
I
OUT =
R
1.20V
R
Load
Figure 3: High Voltage Adjustable Constant Current Source
3
LR8
Typical Performance Curves
Temperature Variation
1.30
V
IN
V
OUT
=1.2V
1.25
VOUT (V)
LR8
ADJ
12V
2.4KΩ
1.0µF
1.20
1.15
1.10
1.05
1.00
-50
-25
0
25
50
75
100
125
T(junction) (°C)
Adjustment Current
12
11
V
IN
V
OUT
=1.2V
IADJ (µA)
LR8
12V,
200V,
400V
ADJ
2.4KΩ
I
ADJ
10
V
IN
= 400V
9
V
IN
= 12V
1.0µF
8
V
IN
= 200V
7
6
-50
-25
0
25
50
75
100
125
T(junction) (°C)
Load Regulation
5.2
V
IN
V
OUT
=5.0V
I
OUT
5.1
LR8
ADJ
25V
18.2KΩ
±1%
6.04KΩ
±1%
1.0µF
R
LOAD
VOUT (V)
5.0
4.9
4.8
0
2
4
6
8
10
IOUT (mA)
4
LR8
Typical Performance Curves
VOUT vs. VIN
6
V
IN
V
OUT
=5.0V
5
LR8
ADJ
0V to 50V
18.2KΩ
±1%
6.04KΩ
±1%
1.0µF
1KΩ
VOUT (V)
4
3
2
1
0
0
10
20
30
40
50
VIN (V)
Ripple Rejection
-65
V
IN
V
OUT
=5.0V
I
OUT
Ripple Rejection Ratio (dB)
-64
LR8
20V
P-P
@ 60Hz
65V
ADJ
6.04KΩ
±1%
1.0µF
R
LOAD
18.2KΩ
±1%
-63
-62
-61
-60
0
2
4
6
8
10
IOUT (mA)
5

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