Buck regulator with spread spectrum modulation reduces EMI noise

The LTC7124 from Analog Devices, which recently acquired Linear Technology, is a 4MHz synchronous dual output buck regulator that 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 of up to 7A.

The switching frequency is user programmable from 500kHz to 4MHz. External clock synchronisation capability is also included for noise-sensitive applications.

The LTC7124 operates from an input voltage of 3.1 to 17V with an output voltage range of 0.6V to 99% of VIN, with high ±1% VOUT accuracy, suitable 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 uses internal N-channel MOSFET switches with RDS (ON) of 80mΩ and 40mΩ to deliver efficiencies up to 95%. The two channels run 180° out-of-phase, minimising the size of both input and output capacitance.

Burst Mode operation is used to maximise light load efficiency, requiring 8µA with both channels enabled and 5.5µA of quiescent current with one channel enabled. For applications requiring the lowest possible noise, the LTC7124 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.

The LTC7124 is available in a thermally enhanced 3 x 5mm QFN-24 package. E- and I-grade versions are guaranteed to operate in temperatures ranging from -40 to 125°C.