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Power/Alternative Energy  

Tiny buck regulator suits single cell apps

Posted: 07 Apr 2008     Print Version  Bookmark and Share

Keywords:synchronous buck regulator  Li-ion  synchronous rectification 

Linear Technology Corp. has rolled the LTC3523/-2, a combination of a 600mA (ISW) synchronous boost and a 400mA (IOUT) synchronous buck regulator in a 3mm x 3mm QFN-16 package. Both the boost and the buck regulators switch at 2.4MHz in the LTC3523-2 (1.2MHz for the LTC3523), and use current mode, synchronous topologies.

The LTC3523/-2 operate from an input voltage range of 1.8V to 5.5V, making them appropriate for single cell Li-ion/polymer or dual-cell alkaline/NiMH applications. In particular, the combination of a buck and a boost makes it suitable for dual-cell alkaline applications, in which a processor 3.3V I/O rail and a 1.2V (or lower) VCORE rail are required. Synchronous rectification enables efficiencies of up to 94 percent and Burst Mode operation lowers quiescent current to only 45µA, providing extended battery run-time in handheld applications. Constant synchronised frequency 1.2MHz (LTC3523) or 2.4MHz (LTC3523-2) operation offers low noise, high efficiency operation. Combined with a 3mm x 3mm QFN-16 package, small inductor and capacitor sizes provide a tiny solution footprint required in handheld applications.

The boost converter in the LTC3523/-2 incorporates an integrated output disconnect function for reliable operation and also regulates when Vin > Vout, extending usable battery runtime. Its output voltage is adjustable between 1.8V and 5.25V. Similarly, the buck converter operates from the same Vin range and can deliver 400mA outputs as low as 0.6V. Both converters offer internal compensation, soft start and have separate Power Good pins. For low noise applications, the Burst Mode feature can be replaced with a lower noise forced continuous mode.

LTC3523EUD and LTC3523EUD-2 are both available from stock in 16-lead QFN packages. Pricing for 1,000-piece quantities starts at Rs.116.46 ($2.95) each.





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