2.5A power manager simplifies Li-ion battery backup

June 08, 2015 // By Graham Prophet
LTC4040 is a complete lithium battery backup power management system for 3.5V to 5V supply rails that must be kept active during a main power failure. Batteries provide considerably more energy than supercapacitors, making them superior for applications which require backup for extended periods of time.

LTC4040 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 the LTC4040 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 for the LTC4040 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.

The LTC4040 also includes optional overvoltage protection (OVP) which protects the IC from input voltages greater than 60V with an external FET. 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 LTC4040’s 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 low profile (0.75 mm) 24-pin 4 x 5 mm QFN package with backside metal pad for thermal performance. The device operates from -40°C to 125°C, in both E and I grades. The LTC4040 costs $2.90 (1000) (E grade).

Linear Technology; www.linear.com/product/LTC4040

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