The LTC3126 is a high efficiency synchronous buck converter with an internal no-loss PowerPath™supporting seamless operation from two separate input power sources. Pin selectable ideal diode-OR and priority input modes with user programmable undervoltage lockout thresholds provide full control over the transition between the input power sources. The fast, automatic switchover provided by the internal PowerPath eliminates the need for hold-up capacitors and minimizes disturbances on the output rail. An active input channel indicator and independent input and output power good signals provide complete feedback of the power system status.A wide 2.4V to 42V input voltage range, 2.5A output current capability and 2μA Burst Mode operation quiescent current facilitate use of the LTC3126 with a wide variety of power sources including supercapacitors, automotive batteries, unregulated wall adapters and single to multicell stacks of most battery chemistries. Additional features include 1μA current in shutdown, internal soft-start and thermal protection. The LTC3126 is available in thermally enhanced 28-lead 4mm × 5mm QFN and 28-lead TSSOP packages.ApplicationsPortable Industrial/Communications Test EquipmentBattery and Supercapacitor Backup PowerAutomotive Power with Battery BackupUninterruptible Power Supplies