Page 1
High Input Voltage
SMPS Start-up / Linear Regulator
Ordering Information
Order Number / Package
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.
LR645
Product marking for TO-243AA:
LR6❋
where ❋ = 2-week alpha date code
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 50µA
❏ 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
Applications
❏ Off-line SMPS startup circuits (pulse loads)
❏ Low power off-line regulators
❏ Regulators for noisy inputs
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.
Absolute Maximum Ratings
Input Voltage 450V
Output Voltage 15.5V
Operating and Storage Temperature –55°C to +150°C
Soldering Temperature* 300°C
*Distance of 1.6mm from case for 10 seconds
For detailed circuit and application information, please refer
to application note AN-H28.
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.
(continued on page 14-3)
Pin Configuration
1
2
3
TAB
TO-243AA
(SOT-89)
1 2 3
TO-92
1
2
3
4
SO-8
+V
IN
TO-92 1 2 3 — —
TO-243AA 1 2, TAB 3 — —
TO-220 1 2, TAB 3 — —
P-DIP 13457
5
GND V
OUT
Trim Gate
TAB
1
2
3
TO-220
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.
1
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LR645
Thermal Characteristics
Package Power Dissipation θ
@ TA = 25°C °C/W °C/W
SO-8 0.31W 156 400
jc
θ
ja
†
Block Diagram
V
IN
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
increase possible on ceramic substrate.
D
†
Trim
–
+
Electrical Characteristics
Test conditions unless otherwise specified: TA = 25°C; VIN = 15 to 450V, C
Symbol Parameter Min Typ Max Unit Conditions
V
OUT
V
OUT
∆V
∆V
V
IN
I
INQ
I
OFF
I
AUX
∆V
e
n
I
PEAK
V
AUX
OUT
OUT
OUT
/∆V
Output Voltage 9.3 10 10.7 V No load
Output Voltage over Temperature
1
9.0 10 11.5 V TJ = -40°C ≤ to + 125°C, No load
Line Regulation 40 200 mV VIN=15V to 400V, No load
Load Regulation 150 400 mV VIN=50V, I
Operating Input Voltage Range 15 450 V
Input Quiescent Current 50 150 µA No Load
VIN Off-State Leakage Current 0.1 10 µAV
Input Current to V
Ripple Rejection Ratio
IN
Noise voltage
Output Peak Current
External Voltage Applied to V
OUT
1
1
2
OUT
50 60 dB 120Hz, No Load
25 µV 0.01 to 100KHz
30 mA C
= 0.01µF
OUT
AUX≥VOUT
200 µAV
AUX≥VOUT
OUT
13.2 V
=0 to 3.0mA
OUT
+1V applied to V
+1V applied to V
= 10µF, VIN = 400V
V
OUT
Gate
GND
OUT
OUT
pin
pin
8-pin, adjustable output voltage version only.
Test conditions unless otherwise specified: TA = 25°C; VIN = 15 to 450V, C
Symbol Parameter Min Typ Max Unit Conditions
V
OUT
∆V
OUT
∆V
OUT
Notes:
1. Guaranteed by design, not tested in production.
2. Pulse test duration < 1msec, Duty cycle < 2%
Output Voltage Trim Range
Load Regulation at 8V trim
Load Regulation at 12V trim
1
1
1
8 12 V No load
200 400 mV VIN=15V, I
100 400 mV VIN=50V, I
2
= 0.01µF
OUT
=0 to 1.0mA
OUT
=0 to 3.0mA
OUT
Page 3
LR645
General Description
(Continued from page 14-1)
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 0.01µF 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
a nominal output voltage of 10V. The auxiliary voltage connected
through a diode to the V
pin of the LR6 will start to increase.
OUT
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
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 0.1µA.
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.
line of the PWM IC with
CC
CC
line
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
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 200KΩ to 300KΩ. This minimizes loading
and optimizes accuracy of the output voltage. Figure 5 uses an
R1 + R2 of 250KΩ.
and Trim pins.
OUT
Figure 1: SMPS Start-Up Circuit
+
15V
to
V
IN
V
OUT
450V
C
IN
C
OUT
GND
–
Figure 2: High Current SMPS Start-Up
+
DN2540
Gate
15V
to
400V
C
LR645LG
IN
V
OUT
Trim
R2
C
OUT
+
5.0V
–
V
=12V
AUX
V
CC
PWM ICLR6
+
5.0V
–
V
=12V
AUX
V
CC
PWM IC
GND
R1
–
Note: When used with the DN25, +VIN is not connected on the LR6.
3
Page 4
LR645
12
10
8
2.5 3.0 4.03.5
Resistor Ratio, R2/R1
Output Voltage
R1 + R2 = 250KΩ
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 fullwave or half-wave rectified. A minimum output capacitance of
0.01µF 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.
Figure 3: Cascading for Precision
Max
C
OUT
.01µF
875
ACSA
5.000V
± .002V @
0 to 3mA
AC Line
(24 to
277VAC)
C
IN
1µF
LR6
P
DISS
=(V
- V
IN
OUT
) x (I
OUT
+ I
MAX QUIESCENT
)
= (400V - 10V) x (3.0mA + 150µA)
= 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
but is typically a few
OUT
hundred milliseconds.
All package types of the LR6 have been characterized for use
with a C
of at least 10µF , and an AC line of 277V.
OUT
Figure 5:
Typical Output Voltage vs. Resistor Ratio
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:
Figure 4:
High Current
Regulator
AC Line
(24 to
277VAC)
C
IN
GND
DN2540N5
Gate
LR645LG
C
OUT
V
OUT
5.0V
Reg
5.0V
+
0 to
150mA
–
©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
11/12/01
1235 Bordeaux Drive, Sunnyvale, CA 94089
TEL: (408) 744-0100 • FAX: (408) 222-4895
4
www.supertex.com
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