Proving the Business Case for the Internet of Things

Linear Technology device keeps power flowing for asset tracking applications

Steve Rogerson
June 16, 2015
A lithium battery backup power management system from California-based Linear Technology can keep power on during failures in fleet and asset tracking applications as well as automotive GPS data loggers and automotive telematics systems.
The LTC4040 is a complete lithium battery backup power management system for 3.5 to 5V supply rails that must be kept active during a main power failure. Batteries provide considerably more energy than supercapacitors, making them better for applications that require backup for extended periods of time.
This device uses an on-chip bidirectional synchronous converter to provide high efficiency battery charging as well as high current, high efficiency backup power. When external power is available, the device operates as a step-down battery charger for single-cell Li-ion or LiFePO4 batteries while giving preference to the system load. When the input supply drops below the adjustable power-fail input (PFI) threshold, it operates as a step-up regulator capable of delivering up to 2.5A to the system output from the backup battery.
During a power fail event, the device’s PowerPath control provides reverse blocking and a seamless switchover between input power and backup power. Typical applications include fleet and asset tracking, automotive GPS data loggers, automotive telematics systems, toll collection systems, security systems, communications systems, industrial backup and USB-powered devices.
It also includes optional overvoltage protection, which protects the IC from input voltages greater than 60V with an external transistor. Its adjustable input current limit function enables operation from a current limited source while prioritising system load current over battery charge current.
An external disconnect switch isolates the primary input supply from the system during backup. The 2.5A battery charger provides eight selectable charge voltages optimised for Li-ion and LiFePO4 batteries. The device also includes input current monitoring, an input power loss indicator and a system power loss indicator.
The LTC4040 is housed in a 0.75mm high 24-pin 4 by 5mm QFN package with backside metal pad to improve thermal performance. It operates from -40 to +125ËšC, in E and I grades.