1
LR645
General Description
The Supertex LR6 is a high input voltage, low output current
linear regulator. It has a 3-terminal fixed output voltage version
available in TO-92, TO-220 and SOT-89 packages as well as an
adjustable voltage version available in 8 pin SOIC package. The
3-terminal version functions like any other low voltage 3-terminal
regulator except it allows the use of much higher input voltages.
When used in a SMPS start-up circuit, it eliminates the need for
large power resistors. In this application, current is drawn from
the high voltage line only during start-up. Only leakage current
flows after start-up thereby reducing the continuous power
dissipation to a few milliwatts.
The adjustable voltage version allows trimming of the output
voltage from 8V to 12V. This version can also be connected to an
external depletion mode MOSFET for increased output current.
When used in conjunction with Supertex depletion mode MOSFET
DN2540N5, up to a 150mA is achieved.
Max. Input Voltage
TO-92
TO-243AA*
TO-220
SO-8
Die
450V
LR645N3
LR645N8
LR645N5
LR645LG LR645ND
*Same as SOT-89. Product supplied on 2000 piece carrier tape reels.
Ordering Information
Features
Accepts inputs from 15V to 450V
Compatible with industry standard PWM ICs.
See application note AN-H28.
Output currents up to 3mA continuous, 30mA peak
Supply current typically 50A
Line regulation typically 0.1mV/V
Output can be trimmed from 8.0V to 12V
Output current can be increased to 150mA with external FET
High Input Voltage
SMPS Start-up / Linear Regulator
(continued on page 14-3)
Absolute Maximum Ratings
Input Voltage
450V
Output Voltage
15.5V
Operating and Storage Temperature
55
C to +150C
Soldering Temperature*
300
C
*Distance of 1.6mm from case for 10 seconds
Applications
Off-line SMPS startup circuits (pulse loads)
Low power off-line regulators
Regulators for noisy inputs
Pin Configuration
+V
IN
GND
V
OUT
Trim
Gate
TO-92
1
2
3
--
--
TO-243AA
1
2, TAB
3
--
--
TO-220
1
2, TAB
3
--
--
P-DIP
1
3
4
5
7
SO-8
5
4
3
2
1
TO-243AA
(SOT-89)
3
2
1
TAB
1 2 3
TO-92
1
2 3
TO-220
TAB
Caution
The LR6 does NOT provide galvanic isolation. When
operated from an AC line, potentially lethal voltages can be
present on the IC. Adequate means of protecting the end
user from such voltages must be provided by the circuit
developer.
For detailed circuit and application information, please refer
to application note AN-H28.
Order Number / Package
Product marking for TO-243AA:
LR6
where
= 2-week alpha date code
11/12/01
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 the latest product specifications, refer to the
Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.
2
+
V
OUT
GND
Gate
V
IN
Trim
Thermal Characteristics
Package
Power Dissipation
jc
ja
@ T
A
= 25
C
C/W
C/W
SO-8
0.31W
156
400
TO-92
0.74W
125
170
TO-220
1.8W
8.3
70
TO-243AA
1.6W
15
78
Mounted on FR5 board, 25mm x 25mm x 1.57mm.
Significant P
D
increase possible on ceramic substrate.
Block Diagram
Symbol
Parameter
Min
Typ
Max
Unit
Conditions
V
OUT
Output Voltage
9.3
10
10.7
V
No load
V
OUT
Output Voltage over Temperature
1
9.0
10
11.5
V
T
J
= -40
C to + 125C, No load
V
OUT
Line Regulation
40
200
mV
V
IN
=15V to 400V, No load
V
OUT
Load Regulation
150
400
mV
V
IN
=50V, I
OUT
=0 to 3.0mA
V
IN
Operating Input Voltage Range
15
450
V
I
INQ
Input Quiescent Current
50
150
A
No Load
I
OFF
V
IN
Off-State Leakage Current
0.1
10
A
V
AUX
V
OUT
+1V applied to V
OUT
pin
I
AUX
Input Current to V
OUT
200
A
V
AUX
V
OUT
+1V applied to V
OUT
pin
V
OUT
/
V
IN
Ripple Rejection Ratio
1
50
60
dB
120Hz, No Load
e
n
Noise voltage
1
25
V
0.01 to 100KHz
I
PEAK
Output Peak Current
2
30
mA
C
OUT
= 10
F, V
IN
= 400V
V
AUX
External Voltage Applied to V
OUT
13.2
V
Electrical Characteristics
Test conditions unless otherwise specified: T
A
= 25
C; V
IN
= 15 to 450V, C
OUT
= 0.01
F
Symbol
Parameter
Min
Typ
Max
Unit
Conditions
V
OUT
Output Voltage Trim Range
1
8
12
V
No load
V
OUT
Load Regulation at 8V trim
1
200
400
mV
V
IN
=15V, I
OUT
=0 to 1.0mA
V
OUT
Load Regulation at 12V trim
1
100
400
mV
V
IN
=50V, I
OUT
=0 to 3.0mA
Notes:
1. Guaranteed by design, not tested in production.
2. Pulse test duration < 1msec, Duty cycle < 2%
8-pin, adjustable output voltage version only.
Test conditions unless otherwise specified: T
A
= 25
C; V
IN
= 15 to 450V, C
OUT
= 0.01
F
LR645
3
PWM IC
LR645LG
GND
R2
R1
Gate
+
15V
to
400V
+
5.0V
V
OUT
Trim
DN2540
C
OUT
C
IN
V
CC
V
AUX
=12V
PWM IC
LR6
GND
+
15V
to
450V
+
5.0V
V
AUX
=12V
V
IN
V
OUT
C
OUT
C
IN
V
CC
LR6: High Current SMPS
Start-Up Circuit
The 8 pin version of the LR6 has connections for an external
depletion-mode MOSFET for higher output current and external
resistors for adjustable output voltage. As shown in Figure 2, the
output current is increased to 150mA by using the Supertex 400V
depletion-mode MOSFET DN2540. The maximum operating
input voltage will be limited by the drain-to-source breakdown
voltage of the external MOSFET, but cannot exceed the 450V
rating of LR6.
The output voltage can be adjusted from 8V to 12V with 2
external resistors, R1 and R2. The ratio of R2/R1 determines the
output voltage. R2 is connected between the V
OUT
and Trim pins.
R1 is connected between Trim and GND pins. Figure 5 is a curve
showing output voltage versus resistor ratio R2/R1. The optimum
range for R1 + R2 is 200K
to 300K. This minimizes loading
and optimizes accuracy of the output voltage. Figure 5 uses an
R1 + R2 of 250K
.
Figure 2: High Current SMPS Start-Up
Figure 1: SMPS Start-Up Circuit
LR6: SMPS Start-Up Circuit
One of the main applications for the LR6 is a start-up circuit for
off-line switch-mode power supplies (SMPS) as shown in Figure
1. A minimum output capacitance of 0.01
F is recommended for
stability. The wide operating input voltage range of the LR6
allows the SMPS to operate and start-up from rectified AC or a
DC voltage 15V to 450V without adjustment.
During start-up, the LR6 powers the V
CC
line of the PWM IC with
a nominal output voltage of 10V. The auxiliary voltage connected
through a diode to the V
OUT
pin of the LR6 will start to increase.
When the auxiliary voltage becomes larger than the output
voltage the LR6 turns OFF its internal high voltage input line and
output voltage allowing the auxiliary voltage to power the V
CC
line
of the PWM IC. The input current drawn by the LR6 from the high
voltage line after start-up will therefore only be leakage current
of the internal MOSFET switch, which is typically 0.1
A.
The 3-terminal version shown in Figure 1 has load regulation
guaranteed from 0 to 3.0mA at a fixed nominal output voltage of
10V. Applications requiring higher output current and/or a different
output voltage can use the 8 pin adjustable version.
General Description
(Continued from page 14-1)
LR645
Note: When used with the DN25, +V
IN
is not connected on the LR6.
4
Power Dissipation Considerations
The LR6 is a true linear regulator. Its power dissipation is
therefore a function of input voltage and output load current. For
example, if the LR6 is providing a continuous load current of 3mA
at 10V while its input voltage is 400V, total dissipation in the LR6
will be:
LR6:Off Line Linear Regulator
Circuits requiring low voltages to operate logic and analog
circuits benefit from the LR6. The conventional use of step down
transformers can be eliminated thereby saving space and cost.
Some examples of these applications are proximity controlled
light switches, street lamp control, and low voltage power supplies
for appliances such as washing machines, dishwashers, and
refrigerators.
The wide operating input voltage range of 15V to 450V as well as
the ripple rejection ratio of 50dB minimum allow the use of small
high voltage input capacitor. The input AC line can be either full-
wave or half-wave rectified. A minimum output capacitance of
0.01
F is recommended for output stability.
Figure 3 shows the LR6 as a pre-regulator to a precision
regulator for high precision regulation. Higher output current is
also possible by using an external depletion-mode MOSFET
DN2540N5 as shown in Figure 4.
LR645
LR6
Max
875
ACSA
5.000V
.002V @
0 to 3mA
AC Line
(24 to
277VAC)
1
F
.01
F
C
OUT
C
IN
Figure 3: Cascading for Precision
12
10
8
2.5
3.0
4.0
3.5
Resistor Ratio, R2/R1
Output Voltage
R1 + R2 = 250K
Figure 5:
Typical Output Voltage vs. Resistor Ratio
AC Line
(24 to
277VAC)
5.0V
0 to
150mA
5.0V
Reg
+
C
OUT
C
IN
V
OUT
Gate
DN2540N5
GND
LR645LG
Figure 4:
High Current
Regulator
P
DISS
=
(V
IN
- V
OUT
) x (I
OUT
+ I
MAX QUIESCENT
)
=
(400V - 10V) x (3.0mA + 150
A)
=
1.23 Watts
The 1.23 watts is for continuous operation. This is within the
dissipation capabilities of the TO-220 and SOT-89 packages.
See Page 14-2, thermal characteristics, for deratings.
For SMPS start-up applications, the output current is usually
required only during start-up. This duration depends upon the
auxiliary supply output capacitor and C
OUT
but is typically a few
hundred milliseconds.
All package types of the LR6 have been characterized for use
with a C
OUT
of at least 10
F , and an AC line of 277V.
1235 Bordeaux Drive, Sunnyvale, CA 94089
TEL: (408) 744-0100 FAX: (408) 222-4895
www.supertex.com
11/12/01
2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
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