Inductorless DC-DC Converter Achieves 500-mA Continuous Output

Eschewing inductors, the LTC3251 spread-spectrum dc-dc converter can deliver up to 500 mA of continuous output current. It operates within a V_IN range of 2.7 to 5.5 V, suiting it for single-cell lithium-ion or multicell nickel-metal-hydride/alkaline applications. The output voltage is resistor-programmable from 0.9 to 1.6 V, enabling the device to drive low-voltage DSPs and microcontrollers. Thanks to switched-capacitor fractional conversion techniques, the LTC3251 attains efficiencies as high as 88%, only slightly lower than that of an equivalent buck switching regulator. The converter's ultra-low noise, high efficiency, and compact footprint suit it for handheld wireless applications that require low noise and maximum battery life without the use of an inductor. The part's switching frequency randomly shifts within the 1.0- to 1.6-MHz frequency range to minimize harmonic switching spikes that can introduce noise into nearby RF circuitry. The LTC3251 offers four operating modes to reduce power consumption: continuous spread spectrum, spread spectrum with Burst mode, Super Burst mode, and shutdown. Operating current measures only 35 µA in Burst mode and 9 µA in Super Burst mode. The LTC3251, which comes in a 10-lead MSOP package, starts at $1.95 each in 1000-piece quantities.