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National step-up DC/DC converters with true shutdown isolation

Posted: 29 Nov 2005 ?? ?Print Version ?Bookmark and Share

Keywords:National Semiconductor? DC/DC converter? LM3500? LM3501?

National Semiconductor Corp. announced two fixed-frequency step-up DC/DC converters with true shutdown isolation. These devices feature a low feedback voltage of 500mV and fully integrated synchronous switching that requires no external Schottky diode.

According to the company, power efficiency of the LM3500 and LM3501 DC/DC converters has been optimized for lighting applications in portable products with single cell Li-ion or 3-cell NiMH battery supplies. Both the LM3500 and LM3501 operate with a fixed 1MHz switching frequency and ceramic input and output capacitors. In addition, high switching frequency, very small external ceramic capacitors and the integration of a diode, provide the customer with a small, low-cost solution.

A single external resistor is used to set the maximum LED current in driver applications. The current can be adjusted using a pulse-width modulation signal on the shutdown pin of the LM3500 or an analog control signal on the CNTRL pin of the LM3501. In shutdown, the converters completely disconnect the input from the output, creating total isolation and preventing any leakage currents from trickling into the LEDs.

Packaged in an 8-bump micro SMD, the LM3500 and LM3501 are designed for driving white LEDs in display backlighting and other lighting applications. The LM3500 costs $1.40 and the LM3501 is priced at $1.51, both in quantities of 1,000. Pb-free package options are also available.

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Related Datasheets
Part Number Description Category
? LM3500 Synchronous Step-up DC/DC Converter for White LED Applications from the PowerWise? Family ICs, Interface
? LM3501 Synchronous Step-up DC/DC Converter for White LED Applications from the PowerWise? Family ICs, Interface



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