Compact dual synchronous buck with spread spectrum modulation reduces EMI

Linear Technology’s new LTC7124, a high efficiency, 4MHz synchronous dual output buck regulator incorporates a constant frequency, peak current mode architecture. Optional spread spectrum frequency modulation is integrated for reducing radiated and conductive EMI noise. The device can deliver up to 3.5A of continuous output current from each channel or generate a 2-phase single output up to 7A in a compact 3mm x 5mm footprint package. The switching frequency is user programmable from 500kHz to 4MHz, enabling the use of tiny, low cost capacitors and inductors; also included is external clock synchronization capability for noise-sensitive applications. The device operates from an input voltage of 3.1V to 17V with an output voltage range of 0.6V to 99% of VIN, with high ±1% VOUT accuracy, ideal for 1-4 cell Li-Ion applications as well as 5V and 12V intermediate bus systems. Other key applications include battery-powered systems, point-of-load supplies, portable instruments and handheld scanners. Each channel of the device uses internal N-channel MOSFET switches with RDS (ON) of only 80mohm and 40mohm to deliver efficiencies as high as 95%. The two channels run 180 degrees out-of-phase, minimizing the size of both input and output capacitance. User-selectable Burst Mode operation is used to maximize light load efficiency, requiring only 8µA with both channels enabled and only 5.5µA of quiescent current with one channel enabled. For applications requiring the lowest possible noise, the device can be configured to run in forced continuous operation, reducing output voltage ripple and potential RF interference. Additional features include input overvoltage and overtemperature protection, power good voltage monitors, independent soft-start capability for each channel, internal or external loop compensation, programmable current limit and short-circuit protection.