The LTC3643 is a bidirectional synchronous step-up charger and step-down converter which efficiently charges a capacitor array up to 40V from an input supply between 3V to 17V. When the input supply falls below the programmable power-fail threshold, the step-up charger operates in reverse as a synchronous step-down regulator to power the system rail from the backup capacitor during this power interuption/failure condition.When charging the backup capacitor, an external low-value sense resistor may be used to maintain an accurate current limit from the input supply or implement PowerPath™functionality.The step-down converter operates at a 1MHz switching frequency, allowing small external components to be used. Low quiescent current during regulation maximizes the energy usage from the backup capacitor.ApplicationsBackup Capacitor SystemsPower Failure Backup SystemsSolid-State Drives