Synchronous step-down regulator offers programmable output current / voltage

The LTC3649 is a new high-efficiency, 60V / 4A synchronous buck regulator from Linear Technology. The device incorporates a constant-frequency current-mode architecture and programmable output current and output voltage, which are set with a single external resistor. The LTC3649 operates from an input voltage range of 3.1V to 60V and provides an adjustable rail-to-rail output voltage range from 0V to 0.5V below VIN, while delivering up to 4A of continuous output current. Its wide input and output voltage range is ideal for a wide range of test, measurement and industrial applications. The LTC3649’s unique design includes an accurate internally generated 50µA current source on the ISET pin, enabling it to deliver outputs as low as 0V with the use of a single external programming resistor. Also, the LTC3649 offers ±0.8% output voltage accuracy and programmable output current with ±4% accuracy without a sense resistor. Its switching frequency is user programmable from 300kHz to 3MHz, enabling the use of tiny, low cost capacitors and inductors. Combined with a 28-lead 4mm x 5mm QFN or thermally enhanced TSSOP package, the LTC3649 offers a compact solution footprint. The LTC3649 uses internal power switches with RDS(ON) of only 100mohm and 50mohm to deliver efficiencies as high as 95%. Burst Mode operation offers high efficiency at light loads, requiring only 440µA of quiescent current. For noise sensitive applications, the LTC3649 can run in forced continuous mode, offering very low output ripple. Additional features include ±4% accurate output current monitoring, a power good voltage monitor, programmable wire drop compensation, external synchronization capability and thermal protection. The LTC3649EUFD is available in a 4mm x 5mm QFN-28, the LTC3649EFE is offered in a 28-lead, thermally-enhanced TSSOP package. Industrial grade versions, the LTC3649IUFD and LTC3649IFE, operate over the -40C to 125C operating junction temperature range.