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LR645 High Input Voltage SMPS Start-up / Linear Regulator
Ordering Information
Order Number / Package Max. Input Voltage 450V TO-92 LR645N3 TO-243AA* LR645N8 TO-220 SO-8 Die Product marking for TO-243AA: LR6 where = 2-week alpha date code
LR645N5 LR645LG LR645ND
*Same as SOT-89. Product supplied on 2000 piece carrier tape reels.
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
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.
Applications
Off-line SMPS startup circuits (pulse loads) Low power off-line regulators Regulators for noisy inputs
(continued on page 14-3)
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.
Pin Configuration
TAB
1 2 3
TAB
TO-243AA (SOT-89)
123
Absolute Maximum Ratings
Input Voltage Output Voltage Operating and Storage Temperature Soldering Temperature*
*Distance of 1.6mm from case for 10 seconds
TO-92
450V 15.5V
5 12 34 1 23
SO-8 +VIN TO-92 TO-243AA 1 1 1 1 GND 2 2, TAB 2, TAB 3 VOUT 3 3 3 4 Trim -- -- -- 5
TO-220
Gate -- -- -- 7
-55C to +150C 300C
For detailed circuit and application information, please refer to application note AN-H28.
11/12/01
TO-220 P-DIP
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.
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LR645
Thermal Characteristics
Package SO-8 TO-92 TO-220 TO-243AA
Block Diagram
ja C/W 400 170 70 78
Power Dissipation @ TA = 25C 0.31W 0.74W 1.8W 1.6W
jc C/W 156 125 8.3 15
VIN
VOUT
Mounted on FR5 board, 25mm x 25mm x 1.57mm. Significant PD increase possible on ceramic substrate.
Trim
- +
Gate
GND
Electrical Characteristics
Test conditions unless otherwise specified: TA = 25C; VIN = 15 to 450V, COUT = 0.01F
Symbol VOUT VOUT VOUT VOUT VIN IINQ IOFF IAUX VOUT/VIN en IPEAK VAUX Output Voltage Output Voltage over Line Regulation Load Regulation Operating Input Voltage Range Input Quiescent Current VIN Off-State Leakage Current Input Current to VOUT Ripple Rejection Ratio Noise voltage Output Peak
1 1
Parameter
Min 9.3
Typ 10 10 40 150
Max 10.7 11.5 200 400 450
Unit V V mV mV V A A A dB V mA No Load No load
Conditions TJ = -40C to + 125C, No load VIN=15V to 400V, No load VIN=50V, IOUT=0 to 3.0mA
Temperature 1
9.0
15 50 0.1
150 10 200
VAUXVOUT+1V applied to VOUT pin VAUXVOUT+1V applied to VOUT pin 120Hz, No Load 0.01 to 100KHz COUT = 10F, VIN = 400V
50
60 25 30 13.2
Current 2
External Voltage Applied to VOUT
V
8-pin, adjustable output voltage version only. Test conditions unless otherwise specified: TA = 25C; VIN = 15 to 450V, COUT = 0.01F
Symbol VOUT VOUT VOUT Parameter Output Voltage Trim Range1 trim1 trim1 Min 8 200 100 Typ Max 12 400 400 Unit V mV mV No load VIN=15V, IOUT=0 to 1.0mA VIN=50V, IOUT=0 to 3.0mA Conditions
Load Regulation at 8V
Load Regulation at 12V
Notes: 1. Guaranteed by design, not tested in production. 2. Pulse test duration < 1msec, Duty cycle < 2%
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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 0.01F 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 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 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 VCC 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 0.1A. 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.
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 VOUT 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 1: SMPS Start-Up Circuit
+ + 5.0V - VAUX=12V 15V to 450V VIN LR6 C IN GND - COUT VOUT VCC PWM IC
Figure 2: High Current SMPS Start-Up
+ DN2540 + 5.0V - Gate 15V to 400V C IN GND -
Note: When used with the DN25, +VIN is not connected on the LR6.
VAUX=12V VOUT VCC R2 Trim R1 PWM IC COUT
LR645LG
3
LR645
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 0.01F 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.
PDISS
= = =
(VIN - VOUT) x (IOUT + IMAX QUIESCENT) (400V - 10V) x (3.0mA + 150A) 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 COUT but is typically a few hundred milliseconds. All package types of the LR6 have been characterized for use with a COUT of at least 10F , and an AC line of 277V.
Figure 5: Typical Output Voltage vs. Resistor Ratio Figure 3: Cascading for Precision
12
LR6 AC Line (24 to 277VAC) CIN 1F
Max 875 ACSA COUT .01F
Output Voltage
5.000V .002V @ 0 to 3mA
10
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:
R1 + R2 = 250K
8 2.5 3.0 3.5 4.0
Resistor Ratio, R2/R1
Figure 4: High Current Regulator
DN2540N5 AC Line (24 to 277VAC) Gate
LR645LG
VOUT COUT
5.0V Reg
5.0V + 0 to 150mA -
CIN
GND
11/12/01
(c)2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
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1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 744-0100 * FAX: (408) 222-4895 www.supertex.com

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