LR745N3-G-P013

LR745 High-Input Voltage SMPS Start-up Features Description • Accepts inputs from 35 to 450V • Output current limiting • For PWM ICs with start-up threshold voltage of 13.9 - 18.0V • Very low power consumption after start-up LR745 is a high input voltage SMPS start-up circuit. LR745 is ideally suited for use with industry standard low-voltage, Pulse-Width Modulation (PWM) ICs having start thresholds of 13.9 to 18.0V. It allows the PWM ICs to be operated from rectified 120 or 240VAC lines, and eliminates the use of power resistors often used for this purpose. Applications • • • • Notebook and laptop computers Telecommunication power supplies Battery chargers Motor controllers  2015 Microchip Technology Inc. The internal circuitry of the LR745 allows the PWM ICs to operate at a VCC voltage below their start-threshold voltage after start-up. The auxiliary voltage can be less than the start-threshold voltage, which allows for improved efficiency. Current from the high voltage line is drawn only during the start-up period. After start-up, the internal, high-voltage line is disconnected from the IC, thereby reducing the continuous power dissipation to a minimum. DS20005394A-page 1 LR745 Package Type VOUT VIN GND TO-92 GND VOUT GND VIN TO-243AA (SOT-89) See Table 2-1 for pin information DS20005394A-page 2  2015 Microchip Technology Inc. LR745 1.0 ELECTRICAL CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS Input Voltage .................................................................................................................................................................................. 450V Output voltage.................................................................................................................................................................................. 25V Operating and storage temperature ............................................................................................................................. -55°C to +150°C Note: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions, above those indicated in the operational listings of this specification, is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. 1.1 ELECTRICAL SPECIFICATIONS TABLE 1-1: Symbol ELECTRICAL CHARACTERISTICS1 Parameter Min Output voltage 18.0 VOUT over temperature 17.7 IOUT Output current limiting 2.0 VIN Operating input voltage range 35 IINQ Input quiescent current VOUT VOFF VRESET Typ Max 24 3.0 Units Conditions V IOUT= 0 24.3 V IOUT= 0, TA= -40°C to +85°C 4.0 mA 450 V 500 µA 12.6 13.25 13.9 V VOFF over temperature 12.3 13.25 14.2 V Output reset voltage 6.3 7.0 7.7 V VRESET over temperature 6.0 7.0 8.0 V TA= -40°C to +85°C VIN= 400V IOFF VIN off-state leakage current 75 µA VAUX External voltage applied to VOUT 22 V IAUX Input current applied to VOUT 500 µA 1 VIN= 400V, IOUT= 0 Output turn off voltage TA= -40°C to +85°C VAUX= 22V Test Conditions unless otherwise specified: TA = 25°C, VIN = 450V TABLE 1-2: THERMAL CHARACTERISTICS Package θja TO-92 132°C/W TO-243AA (SOT-89) 133°C/W  2015 Microchip Technology Inc. DS20005394A-page 3 LR745 2.0 PIN DESCRIPTION The locations of the pins are listed in Package Type. TABLE 2-1: Function VIN PIN DESCRIPTION Description Regulator input. 8 - 450V. GND Ground return for all internal circuitry. This pin must be electrically connected to circuit common. VOUT Regulator output. DS20005394A-page 4  2015 Microchip Technology Inc. LR745 3.0 APPLICATION INFORMATION supplied by C1, causing the VCC voltage decrease. When VCC decreases to 13.25V, LR745 will turn off its output, thereby reducing its input current from 3.0mA to 10s of microamperes. At this point, all 20mA will be supplied by C1. The PWM IC can now operate to a minimum VCC voltage, typically 10V. Figure 3-1 shows a simplified typical configuration of a switch mode power supply, SMPS, using LR745 in the start-up circuit. LR745’s VOUT terminal is connected to the VCC line of a PWM IC. An auxiliary winding on the transformer generates a VCC voltage to power the PWM IC after start-up. LR745 supplies power for the PWM IC only during start-up. After start-up, LR745 turns off and the auxiliary winding supplies power for the PWM IC. Figure 3-2 shows the typical current and voltage waveforms at various stages from power-up to operation powered by the auxiliary winding. 3.1 Once the switching MOSFET starts operating, the energy in the primary winding is transferred to the secondary outputs and the auxiliary winding, thereby building up VAUX. It is necessary to size the VCC storage capacitor, C1, such that VAUX increases to a voltage greater than 10V before VCC decreases to 10V. This allows VAUX to supply the required operating current for the PWM IC. If for some reason the auxiliary voltage does not reach 10V, VCC will continue to decrease. Once VCC goes below 10V, the PWM IC will return to its start-up condition. The PWM IC will now only draw 0.5mA. VCC will continue to decrease but at a much slower rate. Once VCC decreases below 7.0V, LR745 will turn the output, VOUT, back on. VOUT will start charging C1 as described in Stage I. Stage I Once a voltage is applied on VIN, LR745 starts to charge the VCC capacitor, C1. The VCC voltage starts to increase at a rate limited by the internal current limiter of 3.0mA. The PWM IC is in its start-up condition and will typically draw 0.5mA from the VCC line. The VCC voltage will continue to increase until it reaches the PWM IC’s start threshold voltage, typically 16V. 3.2 3.3 Stage II At this stage, LR745 output is turned off and the PWM IC is operating from the VAUX supply. The auxiliary voltage, VAUX, can be designed to vary anywhere between the minimum operating VCC voltage of the PWM IC (10V) to the maximum auxiliary voltage rating of the LR745 (22V). Once VCC reaches 16V, the PWM IC is in its operating condition and will typically draw 20mA, depending on the operating frequency and size of the switching metal–oxide–semiconductor field-effect transistor (MOSFET). The output of LR745, VOUT, is internally current limited to 3.0mA. The remaining 17mA will be FIGURE 3-1: Stage III SIMPLIFIED SMPS USING LR745 High Voltage VIN VAUX IIN IAUX LR7 C2 D2 VCC VOUT PWM IC GND  2015 Microchip Technology Inc. C1 DS20005394A-page 5 LR745 FIGURE 3-2: START-UP WAVEFORMS Stage I 16.0 VOUT (V) 13.5 12.0 8.0 Stage II Stage III PWM IC Start Threshold Voltage LR7 VOFF Trip Point Auxiliary Supply Powers PWM IC 4.0 t 0.0 3.0 IIN (mA) 2.0 1.0 0.0 IIN ≈ 0mA t 12.0 VAUX (V) 8.0 4.0 VAUX = 12V t 0.0 30.0 20.0 IAUX = 20mA IAUX (mA) 10.0 t 0.0 DS20005394A-page 6  2015 Microchip Technology Inc. LR745 3.4 Block Diagram FIGURE 3-3: BLOCK DIAGRAM VIN R4 M1 + 23V - M2 VZ 2.0 - 4.0mA VOUT VREF Reset R1 comp1 + R2 VOUT Q R D CLK Clock comp1 + R3 GND LR745 is a high voltage, switch-mode power supply start-up circuit which has 3 terminals: VIN, GND, and VOUT. An input voltage range of 35 - 450V DC can be applied directly at the input VIN pin. The output voltage, VOUT, is monitored by the 2 comparators: comp1 and comp2. An internal reference, VREF, and resistor divider R1, R2, and R3set the nominal VOUT trip points of 7.0V for comp1 and 13.25V for comp2. When a voltage is applied on VIN, VOUT will start to ramp up from 0V. When VOUT is less than 7.0V, the output of comp1 will be at a logic high state, keeping the D flip-flop in a reset state. The output of the D flip-flop, Q, will be at logic low keeping transistor M2 off. The data input for the D flip-flop, D, is internally connected to a logic high. As VOUT becomes greater than 7.0V, comp1 will change to a logic low state. VOUT will continue to increase, and the constant current source, typically 3.0mA output, will charge an external storage capacitor. As VOUT reaches above 13.25V, the output of comp2 will then switch from a logic high to a logic low state. The D flip-flop’s output does not change state since its clock input is designed to trigger only on a rising edge, logic low to logic high transition. When there is no load connected to the output, the output voltage will continue to increase until it reaches 21.5V, which is the Zener voltage minus the threshold voltage of transistor M1. The Zener voltage is typically 23V, and the threshold voltage of M1 is typically 1.5V. The Zener diode is biased by resistor R4.  2015 Microchip Technology Inc. VOUT will start to decrease when it is connected to an external load greater than the internal constant current source, which is the case when the PWM IC starts up. When VOUT falls below 13.25V, the output of comp2 will switch from a logic low to a logic high. The output of comp2 will clock in a logic 1 into the D flip-flop, causing the D flip-flop’s output, Q, to switch from a logic low to a logic high. Transistor M2 will then be turned on pulling the gate of transistor M1 to ground, thereby turning transistor M1 off. Transistor M1 will remain off as long as VOUT is greater than 7.0V. Once VOUT decreases below 7.0V, comp1 will reset the D flip-flop, thereby turning transistor M2 off and transistor M1 back on. DS20005394A-page 7 LR745 4.0 DESIGN CONSIDERATIONS 4.2 To ensure the best design using LR745, evaluate the value of C1 and the SMPS requirements. 4.1 Calculating the value for C1 Sizing the VCC capacitor, C1, is an important factor. Making C1 too large will cause the SMPS to power up too slowly. However, if too small, C1 will not allow the SMPS to power up due to insufficient charge in the capacitor to power the IC and MOSFET until the auxiliary supply is available. The value of C1 can be approximated by the following equation: 1 ---  N  1 f C 1 = -----------------------------------V START – V MIN Definitions: - f = switching frequency - N = number of clock cycles required to charge VAUX to VMIN value - I = PWM operating current - VSTART = PWM IC start threshold rating - VMIN = PWM IC minimum VCC operating voltage Consider for example, a PWM IC with a switching frequency of 100KHz, operating current of 20mA, start threshold of 16V, and a minimum operating voltage of 10V. If 100 clock cycles are required to charge the auxiliary voltage to 10V, the minimum value of C1 is calculated as follows: SMPS with wide minimum to maximum load An important point is that the LR745’s output voltage, VOUT, must discharge to below the nominal VOFF trip point of 13.25V in order for its output to turn off. If the SMPS requires a wide minimum to maximum output load variation, it will be difficult to guarantee that VCC will fall below 13.25V under minimum load conditions. Consider an SMPS that is required to power small as well as large loads and is also required to power up quickly. Such a SMPS may power up too fast with a small load, not allowing the VCC voltage to fall below 13.25V. For such conditions, the circuit in Figure 4-1 is recommended. In Figure 4-1, the VREF pin of the UC3844 is used to bias the ground pin of the LR745. The VREF pin on the UC3844 is a 5.0V reference, which stays at 0V until the VCC voltage reaches the start threshold voltage. Once VCC reaches the start threshold voltage, VREF will switch digitally from 0V to 5.0V. During start-up, the LR745 will be on, and VCC will start to increase up to 16V. Once VCC reaches16V, the UC3844 will start to operate and VREF will increase from 0V to 5.0V. The LR745 will see an effective VOUT voltage of 11V (16V minus 5.0V) because the ground of the LR745 is now at 5.0V. The LR745 will immediately turn off its output, VOUT, without having to wait for the VCC voltage to decrease. The VREF switching from 0 to 5.0V during start is a common feature in most PWM ICs. 1 ------------------- 100  20mA 100kHz C 1 = ----------------------------------------------------------------16V – 10V C 1 = 3.3F FIGURE 4-1: USING VREF FOR GROUND VOLTAGE VIN LR7 VOUT VCC C1 GND DS20005394A-page 8 PWM IC VREF  2015 Microchip Technology Inc. LR745 5.0 PACKAGING INFORMATION 5.1 Package Marking Information 3-lead TO-92 Example XXXXXX XXXX e3 YWWNNN LR745 N3 e3 513343 Legend: XX...X Y YY WW NNN e3 * Note: Example 3-lead TO-243AA * (SOT-89) XXXYYWW NNN LR7513 343 Product Code or Customer-specific information Year code (last digit of calendar year) Year code (last 2 digits of calendar year) Week code (week of January 1 is week ‘01’) Alphanumeric traceability code Pb-free JEDEC® designator for Matte Tin (Sn) This package is Pb-free. The Pb-free JEDEC designator ( e3 ) can be found on the outer packaging for this package. In the event the full Microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for product code or customer-specific information. Package may or not include the corporate logo.  2015 Microchip Technology Inc. DS20005394A-page 9 LR745 3-Lead TO-243AA (SOT-89) Package Outline (N8) D D1 C E H 1 2 E1 3 L b b1 A e e1 Side View Top View Note: For the most current package drawings, see the Microchip Packaging Specification at www.microchip.com/packaging. Symbol Dimensions (mm) A b b1 C D D1 E E1 MIN 1.40 0.44 0.36 0.35 4.40 1.62 2.29 2.00† NOM - - - - - - - - MAX 1.60 0.56 0.48 0.44 4.60 1.83 2.60 2.29 e 1.50 BSC e1 3.00 BSC H L 3.94 0.73† - - 4.25 1.20 JEDEC Registration TO-243, Variation AA, Issue C, July 1986. † This dimension differs from the JEDEC drawing Drawings not to scale. DS20005394A-page 10  2015 Microchip Technology Inc. LR745 Note: For the most current package drawings, see the Microchip Packaging Specification at www.microchip.com/packaging.  2015 Microchip Technology Inc. DS20005394A-page 11 LR745 APPENDIX A: REVISION HISTORY Revision A (April 2015) • Update file to new format DS20005394A-page 12  2015 Microchip Technology Inc. LR745 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO. Device Device: - XX X - Package Environmental Options LR745 X Media Type = High-Input, Voltage SMPS, Start-up/Linear Regulator Package: N3 N8 = TO-92 (fixed voltage) = TO-243AA (SOT-89) (fixed voltage) Environmental G = Lead (Pb)-free/ROHS-compliant package Media Type: (blank) = 1000/Bag for N3 packages = 2000/Reel for N8 packages P003 = 2000/Reel for N3 package P013 = 2000/Ammo Pack for N3 package  2015 Microchip Technology Inc. Examples: a) LR745N3-G b) LR745N3-G-P003: c) LR745N3-G-P013: d) LR745N8-G TO-92 package, 1000/bag TO-92 package, 2000/reel. TO-92 package, 2000/ammo pack. TO-243AA package, 2000/reel DS20005394A-page 13 Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. 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Trademarks The Microchip name and logo, the Microchip logo, dsPIC, FlashFlex, flexPWR, JukeBlox, KEELOQ, KEELOQ logo, Kleer, LANCheck, MediaLB, MOST, MOST logo, MPLAB, OptoLyzer, PIC, PICSTART, PIC32 logo, RightTouch, SpyNIC, SST, SST Logo, SuperFlash and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. The Embedded Control Solutions Company and mTouch are registered trademarks of Microchip Technology Incorporated in the U.S.A. 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All other trademarks mentioned herein are property of their respective companies. © 2015, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved. ISBN: 978-1-63277-243-5 QUALITY MANAGEMENT SYSTEM CERTIFIED BY DNV == ISO/TS 16949 == DS20005394A-page 14 Microchip received ISO/TS-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona; Gresham, Oregon and design centers in California and India. The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified.  2015 Microchip Technology Inc. Worldwide Sales and Service AMERICAS ASIA/PACIFIC ASIA/PACIFIC EUROPE Corporate Office 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7200 Fax: 480-792-7277 Technical Support: http://www.microchip.com/ support Web Address: www.microchip.com Asia Pacific Office Suites 3707-14, 37th Floor Tower 6, The Gateway Harbour City, Kowloon China - Xiamen Tel: 86-592-2388138 Fax: 86-592-2388130 Austria - Wels Tel: 43-7242-2244-39 Fax: 43-7242-2244-393 China - Zhuhai Tel: 86-756-3210040 Fax: 86-756-3210049 Denmark - Copenhagen Tel: 45-4450-2828 Fax: 45-4485-2829 India - Bangalore Tel: 91-80-3090-4444 Fax: 91-80-3090-4123 France - Paris Tel: 33-1-69-53-63-20 Fax: 33-1-69-30-90-79 India - New Delhi Tel: 91-11-4160-8631 Fax: 91-11-4160-8632 Germany - Dusseldorf Tel: 49-2129-3766400 Atlanta Duluth, GA Tel: 678-957-9614 Fax: 678-957-1455 Hong Kong Tel: 852-2943-5100 Fax: 852-2401-3431 Australia - Sydney Tel: 61-2-9868-6733 Fax: 61-2-9868-6755 China - Beijing Tel: 86-10-8569-7000 Fax: 86-10-8528-2104 Austin, TX Tel: 512-257-3370 China - Chengdu Tel: 86-28-8665-5511 Fax: 86-28-8665-7889 Boston Westborough, MA Tel: 774-760-0087 Fax: 774-760-0088 China - Chongqing Tel: 86-23-8980-9588 Fax: 86-23-8980-9500 Chicago Itasca, IL Tel: 630-285-0071 Fax: 630-285-0075 Cleveland Independence, OH Tel: 216-447-0464 Fax: 216-447-0643 Dallas Addison, TX Tel: 972-818-7423 Fax: 972-818-2924 Detroit Novi, MI Tel: 248-848-4000 Houston, TX Tel: 281-894-5983 Indianapolis Noblesville, IN Tel: 317-773-8323 Fax: 317-773-5453 Los Angeles Mission Viejo, CA Tel: 949-462-9523 Fax: 949-462-9608 New York, NY Tel: 631-435-6000 San Jose, CA Tel: 408-735-9110 Canada - Toronto Tel: 905-673-0699 Fax: 905-673-6509 China - Dongguan Tel: 86-769-8702-9880 China - Hangzhou Tel: 86-571-8792-8115 Fax: 86-571-8792-8116 India - Pune Tel: 91-20-3019-1500 Japan - Osaka Tel: 81-6-6152-7160 Fax: 81-6-6152-9310 Japan - Tokyo Tel: 81-3-6880- 3770 Fax: 81-3-6880-3771 Korea - Daegu Tel: 82-53-744-4301 Fax: 82-53-744-4302 China - Hong Kong SAR Tel: 852-2943-5100 Fax: 852-2401-3431 Korea - Seoul Tel: 82-2-554-7200 Fax: 82-2-558-5932 or 82-2-558-5934 China - Nanjing Tel: 86-25-8473-2460 Fax: 86-25-8473-2470 Malaysia - Kuala Lumpur Tel: 60-3-6201-9857 Fax: 60-3-6201-9859 China - Qingdao Tel: 86-532-8502-7355 Fax: 86-532-8502-7205 Malaysia - Penang Tel: 60-4-227-8870 Fax: 60-4-227-4068 China - Shanghai Tel: 86-21-5407-5533 Fax: 86-21-5407-5066 Philippines - Manila Tel: 63-2-634-9065 Fax: 63-2-634-9069 China - Shenyang Tel: 86-24-2334-2829 Fax: 86-24-2334-2393 Singapore Tel: 65-6334-8870 Fax: 65-6334-8850 China - Shenzhen Tel: 86-755-8864-2200 Fax: 86-755-8203-1760 Taiwan - Hsin Chu Tel: 886-3-5778-366 Fax: 886-3-5770-955 China - Wuhan Tel: 86-27-5980-5300 Fax: 86-27-5980-5118 Taiwan - Kaohsiung Tel: 886-7-213-7828 China - Xian Tel: 86-29-8833-7252 Fax: 86-29-8833-7256 Germany - Munich Tel: 49-89-627-144-0 Fax: 49-89-627-144-44 Germany - Pforzheim Tel: 49-7231-424750 Italy - Milan Tel: 39-0331-742611 Fax: 39-0331-466781 Italy - Venice Tel: 39-049-7625286 Netherlands - Drunen Tel: 31-416-690399 Fax: 31-416-690340 Poland - Warsaw Tel: 48-22-3325737 Spain - Madrid Tel: 34-91-708-08-90 Fax: 34-91-708-08-91 Sweden - Stockholm Tel: 46-8-5090-4654 UK - Wokingham Tel: 44-118-921-5800 Fax: 44-118-921-5820 Taiwan - Taipei Tel: 886-2-2508-8600 Fax: 886-2-2508-0102 Thailand - Bangkok Tel: 66-2-694-1351 Fax: 66-2-694-1350 01/27/15 DS20005394A-page 15  2015 Microchip Technology Inc.