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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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LM2791 Datenblatt(PDF) 9 Page - Texas Instruments |
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LM2791 Datenblatt(HTML) 9 Page - Texas Instruments |
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9 / 18 page  LM2791 www.ti.com SNVS156M – FEBRUARY 2001 – REVISED MAY 2013 Table 1. Low ESR Capacitor Manufactures Manufacturer Contact website TDK (847) 803 6100 www.component.tdk.com MuRata (800) 831 9172 www.murata.com Taiyo Yuden (800) 348 2496 www.t-yuden.com SCHOTTKY DIODE SELECTION A schottky diode (D1) must be used between VIN and POUT for proper operation. During start-up, the low voltage drop across this diode is used to charge COUT and start the oscillator. It is necessary to protect the device from turning-on its own parasitic diode and potentially latching-up. As a result, it is important to select a schottky diode that will carry at least 200mA or higher current to charge the output capacitor during start-up. A schottky diode like 1N5817 can be used for most applications or a surface mount diode such as BAT54-series and MA2J704 used to reduce the circuit size. Table 2 below lists suggested schottky diode manufactures. Table 2. Diode Manufactures Manufacturer Contact Schottky Diodes ON Semiconductor (800) 344 3860 www.onsemi.con Phillips Semiconductors (800) 234 7381 www.philipssemiconduc tor.com Panasonic Semiconductor (408) 945 5622 www.panasonic.com LED SELECTION The LM2791 is designed to drive LEDs with a forward voltage of about 3.0V to 4.0V or higher. The typical and maximum VF depends highly on the manufacturer and their technology. Table 3 lists two suggested manufactures and example part numbers. Each supplier makes many LEDs that work well with the LM2791. The LEDs suggested below are in a surface mount package and TOPLED or SIDEVIEW configuration with a maximum forward current of 20mA. These diodes also come in SIDELED or SIDEVIEW configuration and various chromaticity groups. For applications that demand color and brightness matching, care must be taken to select LEDs from the same chromaticity group. Forward current matching is assured over the LED process variations due to the constant current output of the LM2791. For best fit selection for an application, consult the manufacturer for detailed information. Table 3. White LED Selection: Component Manufacture Contact LWT673/LWT67C Osram www.osram-os.com NSCW100/ NSCW215 Nichia www.nichia.com ISET PIN An external resistor, RSET, sets the mirror current that is required to provide a constant current through the LEDs. The current through RSET and the LED is set by the internal current mirror circuitry with a ratio of 25:1 The currents through each LED are matched within 0.3%. RSET should be chosen not to exceed the maximum current delivery capability of the device. Table 4 shows a list of RSET values when maximum BRGT = 0V is applied. For other BRGT voltages, RSET can be calculated using this formula: RSET = (((BRGT * 0.42) + VOFFSET))/(ILED)* 25 (1) Table 4. RSETSelections ( when BRGT pin = 0V) ILED per LED *RSET 15mA 330 Ω 10mA 500 Ω 5mA 1K Copyright © 2001–2013, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: LM2791 Not Recommended For New Designs |
Ähnliche Teilenummer - LM2791 |
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Ähnliche Beschreibung - LM2791 |
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