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LR Series: Selecting high input voltage start-up ICs for SMPS

Posted: 07 May 2002     Print Version  Bookmark and Share

Keywords:power 

/ARTICLES/2002MAY/2002MAY07_ICD_AMD_POW_AN02.PDF

1 Selecting High Input Voltage Start-Up ICs for SMPS LR Series Application Note AN-H28 The chart shown below is a list of popular industry standard PWM ICs. Either the LR6 or LR7 is recommended to power these PWM ICs directly from a high voltage bus up to 450VDC. The majority of devices in this selector guide can utilize the LR6 or the LR7 without any additional components. However, the start voltages for some PWM ICs require an additional diode or a zener diode. One asterisk in the start-up device column indicates the LR6 is to be used with a diode in series to ground as shown in Figure 1 below. Two asterisks indicate the LR6 requires a zener diode in series to ground as shown in Figure 2. Supertex LR6 and LR7 are high input voltage switch mode power supply (SMPS) start-up circuit ICs. These start-up ICs allow industry standard low voltage PWM ICs to be operated from rectified utility power lines, e.g. 120VAC or 240VAC, eliminating the use of power resistors often used for this purpose. Current from the high voltage line is drawn only during the start-up period. The LR6 is designed for PWM ICs with low start threshold voltages whereas the LR7 is suitable for PWM ICs with high start threshold voltages. Please refer to the LR6 and LR7 data sheets for detailed information and specifications. Industry Standard IC Start Threshold Voltage Stop Voltage Start-up Device UC1823 8.8 to 9.6 7.6 to 9.2 LR6* UC2823 UC3823 UC1823A/25A 8.4 to 9.6 7.2 to 9.2 LR6* UC2823A/25A UC3823A/25A UC1823B/25B 14 to 17 9.0 to 10 LR7 UC2823B/25B UC3823B/25B UC1824 8.8 to 9.6 7.6 to 9.2 LR6* UC2824 UC3824 VOUT VIN LR6 PWM IC VCC GND C VOUT VIN PWM IC VCC GND VZ C + 5.1V - LR6 Figure 1: Adding a series low voltage diode Figure 2: Adding a series 5.1V zener diode 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 LR Series Applications * Add a diode in series with the ground pin of the LR6 to ground. ** Add a 5.1V zener diode in series with the ground pin of the LR6 to ground. Industry Standard IC Start Threshold Voltage Stop Voltage Start-up Device UC1825 8.8 to 9.6 7.6 to 9.2 LR6* UC2825 UC3825 UC1842/44 15 to 17 9.0 to 11 LR7 UC2842/44 UC3842/44 14.5 to 17.5 8.5 to 11.5 LR7 UC1843/45 9.0 to 11 7.0 to 8.2 LR6** UC2843/45 UC3843/45 8.5 to 11.5 7.0 to 8.2 LR6** UC1842A/44A 15 to 17 9.0 to 11 LR7 UC2842A/44A UC3842A/44A 14.5 to 17.5 8.5 to 11.5 LR7 UC1843A/45A 7.8 to 9.0 7.0 to 8.2 LR6 UC2843A/45A UC3843A/45A UC1848 11.5 to 14 9.0 to 11.5 LR6** UC2848 UC3848 UC1854 14.5 to 17.5 9.0 to 11 LR7 UC2854 UC3854 UC1854A 16 to 17.5 9.0 to 10 LR7 UC2854A UC3854A UC1854B 10.5 to 10.8 9.0 to 10 LR6** UC2854B UC3854B UC1860 16 to 18.5 9.5 to 12 LR7 UC2860 UC3860 UC1861/62/65/66 15 to 18 9.5 to 11.5 LR7 UC2861/62/65/66 UC3861/62/65/66 UC1863/64/67/68 7.0 to 9.0 6.0 to 8.0 LR6 UC2863/64/67/68 UC3863/64/67/68 UC1875/77 10.75 9.25 LR6** UC2875/77 UC3875/77 UC1876/78 15.25 9.25 LR7 UC2876/78 UC3876/78 UC1891/93 15 to 16 9.0 to 10 LR7 UC2891/93 UC3891/93 UC1892/94 11 to 11.5 9.0 to 10 LR6** UC2892/94 UC3892/94 UCC1800 6.6 to 7.8 6.3 to 7.5 LR6 UCC2800 UCC3800 3 LR Series Applications Industry Standard IC Start Threshold Voltage Stop Voltage Start-up Device UCC1806 6.5 to 8.0 5.75 to 7.25 LR6 UCC2806 UCC3806 UC1855A 16 to 17.5 9.0 to 10 LR7 UC2855A UC3855A UCC1855B 10.5 to 10.8 9.0 to 10 LR6** UCC2855B UCC3855B ML1825 8.8 to 9.6 7.6 to 9.2 LR6* ML4809/10/11 15 to 17 7.5 to 10.5 LR7 ML4812/13 15 to 17 9.0 to 11 LR7 ML4815 13.4 9.8 LR6** ML4819 15 to 17 9.0 to 11 LR7 ML4823 8.8 to 9.6 7.6 to 9.2 LR6* ML4824 12 to 14 9.0 to 11 LR6** ML4825 8.8 to 9.6 7.6 to 9.2 LR6* LT1103/1105 14.5 to 17.5 5.0 to 8.0 LR7 LT1241 9.0 to 10.2 7.0 to 8.2 LR6** LT1242/44/46 15 to 17 9.0 to 11 LR7 LT1243/45 7.8 to 9.0 7.0 to 8.2 LR6 LT1248/49 15.5 to 17.5 9.5 to 11.5 LR7 * Add a diode in series with the ground pin of the LR6 to ground. ** Add a 5.1V zener diode in series with the ground pin of the LR6 to ground. 1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 744-0100 7 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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