The LTC4041 is a complete supercapacitor backup system for 2.9V to 5.5V supply rails. It contains a high current step-down DC/DC converter to charge a single supercapacitor or two supercapacitors in series. When input power is unavailable, the step-down regulator operates in reverse as a step-up regulator to backup the system output from the supercapacitor(s). The LTC4041’s adjustable input current limit function reduces charge current to protect the input supply from overload while an external disconnect switch isolates the input supply during backup. When the input supply drops below the adjustable PFI threshold, the 2.5A boost regulator delivers power from the supercapacitor to the system output. An optional input overvoltage protection (OVP) circuit protects the LTC4041 from high voltage damage at the VIN pin. An internal supercapacitor balancing circuit maintains equal voltages across each supercapacitor and limits the maximum voltage of each supercapacitor to a pre-determined value. The LTC4041 is available in a low profile (0.75mm) 24-Lead 4mm × 5mm QFN package. Applications * Ride-Through “Dying Gasp” Supplies * High Current Ride-Through 3V to 5V UPS * Power Meters/Industrial Alarms * Servers/Solid State Drives * 2.5A Step-Down Supercapacitor Charger and 2.5A Step-Up Backup Supply * 6.5A Switches for 2.5A Backup from One Supercapacitor or Two in Series * Input Current Limit Prioritizes Load over Charge Current * Input Disconnect Switch Isolates Input During Backup * Automatic Seamless Switch-Over to Backup Mode