Highly integrated 2.5A Backup Power Manager simplifies lithium-ion battery backup systems

     Linear Technology Corporation introduces the LTC4040, a complete lithium-ion battery backup power management system for 3.5V to 5V power rails, which must remain active in the event of a primary power failure. Batteries provide much more energy than supercapacitors, making them an advantage for applications that require backups to extend operating time. The LTC4040 comes in a flat (0.75mm) 24-pin 4mm x 5mm QFN package with underside metal pads for superior thermal performance. Both the Class E and Class I versions of the device operate in the temperature range -40 °C to 125°C.

     The LTC4040 offers high-efficiency battery charging and high-current, high-efficiency backup power with a built-in bi-directional synchronous converter. When an external power source is available, the device works as a step-down battery charger for a single lithium-ion or LiFePO4 battery while prioritizing powering the system load. When the input power drops below the Adjustable Power Fault Input (PFI) threshold, the LTC4040 operates as a boost regulator capable of delivering up to 2.5A current from the backup battery to the system output.

     In the event of a power failure, the device's PowerPath™ control provides reverse isolation and seamless switching between the input and backup power supplies. Typical applications of the LTC4040 include fleet and asset tracking, automotive GPS data loggers, in-vehicle multimedia systems, toll systems, security systems, communications systems, industrial backup, and USB-powered devices.

     The LTC4040 also includes optional overvoltage protection (OVP) to protect the IC with an external FET against input voltages higher than 60V. Its adjustable input current limiting function allows operation with current-limited power supplies while prioritizing system load current over battery charge current. An external disconnect switch isolates the main input power from the system during backup. The LTC4040's 2.5A battery charger offers eight optional charging voltages optimized for lithium-ion and LiFePO4 batteries. The device also includes input current monitoring, input power consumption indicator, and system power consumption indicator.