New Standby Manager Power Solution

Now that we have made it clear that supercapacitors, batteries and/or a combination of the two can be used as a backup power source for almost all electronic systems, what solutions are available?

First, any IC solution would require a complete lithium-ion battery backup power management system that must be able to power the 3.5 V to 5 V rails in the event of a mains failure. Batteries provide much more energy than supercapacitors, so applications that require a backup power supply for long periods of time are more suitable for use with batteries. Accordingly, any IC solution would require an on-chip bidirectional synchronous converter to efficiently charge the backup battery; if the main supply rail is interrupted, it can also provide high current backup power to the downstream load. Therefore, when an external power supply is available, the device will act as a buck battery charger for a single-cell Li-Ion or LiFePO4 battery while giving priority to the system load. However, if the input supply suddenly drops below the adjustable power fail input (PFI) threshold, the IC will need to act as a boost regulator to provide several amps of current from the backup battery to the system output. Therefore, in the event of a power failure, the IC will need to perform power path control to provide reverse blocking and seamless switching between input and backup power. Typical applications for such ICs include fleet and asset tracking, automotive GPS data loggers, automotive telematics systems, toll collection systems, security systems, communication systems, industrial backup power supplies, and USB powered devices.

The LTC4040 also features an optional overvoltage protection (OVP) feature that protects the IC from input voltages above 60V through an external FET. Its adjustable input current limiting function supports the use of current-limited power supply, while the system load current takes precedence over the battery charging current. The external disconnect switch isolates the main input power from the system during standby power. The LTC4040's 2.5 A battery charger offers eight optional charging voltages optimized for Li-Ion and LiFePO4 batteries. The device also features input current monitoring, an input power loss indicator, and a system power loss indicator.

Similar to the battery is a super capacitor. However, supercapacitors do not support long-term loss of mains, but they are an excellent choice for systems that require high-power, short-term backup power. Therefore, any IC that supports such applications typically needs to be able to support 2.9 V to 5.5 V supply rails during mains interruptions. It is well known that supercapacitors have a higher power density than batteries, making them ideal for systems that require high peak power backup power in a short period of time.