IC manages backup-battery switchover
Linear Technology’s LTC4420 dual-input monolithic power prioritizer for 1.8-V to 18-V systems ensures smooth backup switchover to keep critical circuitry alive during brownout and power-loss conditions. Its 18-V operating capability accommodates a wide range of power sources, including wall adapters, USB ports, supercapacitors, and stacked batteries with lithium-ion, alkaline, or NiMH cells.
Unlike other products, the LTC4420 does not require the backup supply voltage to be lower than the main supply voltage. Internal 500-mA (minimum) current-limited switches multiplex from the primary to the backup supply when the primary voltage falls below the adjustable switchover threshold. Break-before-make switch control blocks reverse and cross conduction currents, while minimizing output voltage droop.
By reducing device operating current to 3.6 µA and the backup supply’s standby current drain to 0.32 µA, the LTC4420 extends runtime in portable battery-operated systems.
The backup supply’s resistive divider is connected to a strobed ground with a duty cycle that is adjustable down to 0.0015%. An optional undervoltage disconnect prevents deeply discharged batteries. The LTC4420 comes in 12-pin MSOP and 3×3-mm DFN packages, specified over the commercial and industrial temperature ranges. Prices start at $2.95 each in lots of 1000 units.
Linear Technology, www.linear.com