Supertex inc.
High Input Voltage SMPS
Start-up / Linear Regulator
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LR645
Features
Accepts inputs from 15 to 450V
Output currents up to 3.0mA continuous, 30mA peak
Supply current typically 50µA
Line regulation typically 0.1mV/V
Output can be trimmed from 8.0 to 12V
Output current can be increased to 150mA with
external FET
General Description
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Off-line SMPS startup circuits (pulse loads)
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Low power off-line regulators
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Regulators for noisy inputs
Applications
The Supertex LR645 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 an 8-lead
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 8.0 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, an output current of up to 150mA
is achieved.
Caution!
The LR645 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 de-
veloper.
Ordering Information
Part Number
LR645LG-G
LR645N3-G
LR645N3-G P002
LR645N3-G P003
LR645N3-G P005
LR645N3-G P013
LR645N3-G P014
LR645N5-G
LR645N8-G
Package Options
8-Lead SOIC
TO-92
TO-92
TO-92
TO-92
TO-92
TO-92
TO-220
TO-243AA (SOT-89)
Packing
2500/Reel
1000/Bag
2000/Reel
2000/Reel
2000/Reel
2000/Reel
2000/Reel
50/Tube
2000/Reel
Pin Configuration
GATE
NC
TRIM
NC
VOUT
GND
NC
+VIN
VOUT
VIN
GND
8-Lead SOIC
GND
TO-92
GND
VOUT
+VIN
GND
VOUT
GND
VIN
TO-220
TO-243AA (SOT-89)
-G denotes a lead (Pb)-free / RoHS compliant package
Refer to ‘P0xx’ Tape & Reel Specs for P002, P003, P005, P013, and
P014 TO-92 Taping Specifications and Winding Styles
Typical Thermal Characteristics
Package
θ
ja
101
O
C/W
132
O
C/W
29
O
C/W
133
O
C/W
Power Dissipation
@T
A
= 25
O
C
Absolute Maximum Ratings
Parameter
Input voltage
Output voltage
Operating and storage temperature
Value
450V
15.5V
-55°C to +150 C
O
8-Lead SOIC
TO-92
TO-220
TO-243AA (SOT-89)
0.31
0.74
1.8
1.6
Absolute Maximum Ratings are those values beyond which damage to the device
may occur. Functional operation under these conditions is not implied. Continuous
operation of the device at the absolute rating level may affect device reliability. All
voltages are referenced to device ground.
Doc.# DSFP-LR645
A062113
* Mounted on FR5 board; 25mm x 25mm x 1.57mm
Significant P
D
increase possible on ceramic substrate
Supertex inc.
www.supertex.com
LR645
Package Marking
LR645
YYWW
LLLL
YY = Year Sealed
WW = Week Sealed
L = Lot Number
= “Green” Packaging
Si
L R
6 4 5
YWLL
8-Lead SOIC
Packages may or may not include the following marks: Si or
Top Marking
LR645N5
LLLLLLLLL
YYWW
Y = Last Digit of Year Sealed
W = Code for Week Sealed
L = Lot Number
= “Green” Packaging
TO-92
Packages may or may not include the following marks: Si or
L = Lot Number
YY = Year Sealed
WW = Week Sealed
= “Green” Packaging
TO-220
LR6W
W = Code for Week Sealed
= “Green” Packaging
TO-243AA (SOT-89)
Packages may or may not include the following marks: Si or
Packages may or may not include the following marks: Si or
Electrical Characteristics
Sym
V
OUT
ΔV
OUT
V
IN
I
INQ
I
OFF
I
AUX
ΔV
OUT
/ΔV
IN
e
n
I
PEAK
V
AUX
Parameter
Output voltage
(Test conditions unless otherwise specified: T
A
= 25°C; V
IN
= 15 to 450V, C
OUT
= 0.01µF)
Min
9.3
9.0
-
-
15
-
-
-
50
-
-
-
Typ
10
10
40
150
-
50
0.1
-
60
25
30
-
Max
10.7
11.5
200
400
450
150
10
200
-
-
-
13.2
Units
V
V
mV
mV
V
µA
µA
µA
dB
µV
mA
V
Conditions
No load
T
J
= - 40 to +125°C, No load
V
IN
= 15 to 400V, No load
V
IN
= 50V, I
OUT
= 0 to 3.0mA
---
No Load
V
AUX
≥ V
OUT
+1V applied to V
OUT
pin
V
AUX
≥ V
OUT
+1V applied to V
OUT
pin
120Hz, No Load
0.01 to 100KHz
C
OUT
= 10µF, V
IN
= 400V
---
Output voltage over temperature
1
Line regulation
Load regulation
Operating input voltage range
Input quiescent current
V
IN
off-state leakage current
Input current to V
OUT
Ripple rejection ratio
1
Noise voltage
1
Output peak current
2
External voltage applied to V
OUT
Test conditions unless otherwise specified: T
A
= 25°C; V
IN
= 15 to 450V, C
OUT
= 0.01µF
8-lead, adjustable output voltage version only:
V
OUT
ΔV
OUT
Output regulation trim range
1
Load regulation at 8V trim
1
Load regulation at 12V trim
1
8
-
-
-
200
100
12
400
400
V
mV
mV
No load
V
IN
= 15V, I
OUT
= 0 to 1.0mA
V
IN
= 50V, I
OUT
= 0 to 3.0mA
Notes:
1. Guaranteed by design.
2. Pulse test duration <1.0msec, duty cycle <2%.
Doc.# DSFP-LR645
A062113
2
Supertex inc.
www.supertex.com
LR645
LR645 Block Diagram
VIN
LR645
VOUT
TRIM
–
+
GATE
GND
LR645: SMPS Start-Up Circuit
One of the main applications for the LR645 is a start-up
circuit for off-line switch-mode power supplies (SMPS), as
shown in Figure1. A minimum output capacitance of 0.01µF
is recommended for stability. The wide operating input volt-
age range of the LR645 allows the SMPS to operate and
start-up from rectified AC or a DC voltage of 15 to 450V with-
out adjustment.
During start-up, the LR645 powers the VCC line of the PWM
IC with a nominal output voltage of 10V. The auxiliary voltage
connected through a diode to the VOUT pin of the LR645 will
start to increase. When the auxiliary voltage becomes larger
than the output voltage the LR645 turns OFF its internal high
voltage input line and output voltage, allowing the auxiliary
voltage to power the VCC line of the PWM IC. The input
current drawn by the LR645 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 regula-
tion 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.
Figure 1: SMPS Start-Up Circuit
+
+
5.0V
-
V
AUX
= 12V
15 - 450V
VIN
C
IN
LR6
GND
VCC
C
OUT
PWM IC
-
Doc.# DSFP-LR645
A062113
3
Supertex inc.
www.supertex.com
LR645
LR645: High Current SMPS Start-Up Circuit
The 8 lead version of the LR645 has connections for an ex-
ternal 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 the LR645.
The output voltage can be adjusted from 8 to 12V with 2 ex-
ternal 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 200KΩ to
300KΩ. This minimizes loading and optimizes accuracy of
the output voltage. Figure 5 uses an R1 + R2 of 250KΩ.
Figure 2: High Current SMPS Start-Up Circuit
+
DN2540
+
5.0V
–
15V
to
400V
C
IN
GATE
VOUT
VCC
R2
C
OUT
V
AUX
= 12V
LR645
TRIM
GND
PWM IC
R1
–
Note:
When used with the DN25, +V
IN
is not connected on the LR6.
LR645: Off Line Linear Regulator
Circuits requiring low voltages to operate logic and analog
circuits benefit from the LR645. 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 controls, and
low voltage power supplies for appliances such as washing
machines, dishwashers, and refrigerators.
The wide operating input voltage range of 15 to 450V as well
as the ripple rejection ratio of 50dB minimum allows the use
of a small, high voltage input capacitor. The input AC line can
be either full-wave or half-wave rectified. A minimum output
capacitance of 0.01µF is recommended for output stability.
Figure 3 shows the LR645 as a pre-regulator to a precision-
regulator for high precision regulation. Higher output cur-
rent is also possible by using an external depletion-mode
MOSFET DN2540N5 as shown in Figure 4.
Power Dissipation Considerations
The LR645 is a true linear regulator. Its power dissipation is-
therefore a function of input voltage and output load current.
Forexample, if the LR645 is providing a continuous load cur-
rent of 3mAat 10V while its input voltage is 400V, total dis-
sipation in the LR645 will be:
P
DISS
= (V
IN
- V
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 packag-
es. See the thermal characteristics chart on page 2 for derat-
ings. 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 LR645 have been characterized for use with a C
OUT
of at
least 10µF, and an AC line of 277V.
Figure 3: Cascading for Precision
LR6
AC Line
24V - 277V
C
IN
1.0µF
Max
875
ACSA
C
OUT
0.1µF
5.000V
± 0.002V
@
0 to 3mA
Doc.# DSFP-LR645
A062113
4
Supertex inc.
www.supertex.com
LR645
Figure 4: High Current Regulation
DN2540N5
AC Line
24 - 277V
C
IN
GATE
LR645
V
OUT
5.0V
REG
5.0V
+
0 - 150mA
-
C
OUT
GND
Figure 5: Typical Output Voltage vs Resistor Ratio
12
Output Voltage (V)
10
R1 + R2 = 250kΩ
8
2.5
3.0
3.5
4.0
Resistor Ratio (R2/R1)
Doc.# DSFP-LR645
A062113
5
Supertex inc.
www.supertex.com
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