Dual Input Priority Sequencer Provides Low Quiescent Current, Backup Power Switching Solutions

Linear Technology Corporation, a division of Analog Devices, Inc., introduced the LTC4418, a dual-input power prioritizer for 2.5V to 40V systems. In order to achieve portability, maintain memory operation during undervoltage, and ensure smooth shutdown in the event of power loss, the electronic system uses batteries and capacitors as backup power. The LTC4418 typically uses a higher priority main power source such as a wall adapter or main battery to power the load and switch to a backup power source (usually a battery or large value capacitor) in the event of a main power supply undervoltage or missing power supply. The ability to operate at input voltages up to 40V allows the LTC4418 to accommodate a variety of power sources such as wall adapters, USB ports, supercapacitors, and multi-cell lead-acid, lithium-ion, or nickel-metal hydride (NiMH) batteries. The 26μA low operating quiescent current and a shutdown mode make the LTC4418 ideal for portable battery-powered systems.

The external back-to-back P-channel MOSFET switch is multiplexed from the main power supply to the backup power input when the main supply voltage is removed from the effective voltage window setting with adjustable and precise overvoltage and undervoltage thresholds. Carefully designed "break before make" fast switching control isolates reverse and cross conduction currents while minimizing output voltage drop. An external capacitor is responsible for setting the time that a power supply must stay within its voltage window before it is considered "active." Up to -42V inverting input voltage can be isolated to protect the load.

The prioritization of more than two power supplies can be accomplished by any combination of cascaded LTC4418 and three-channel power device LTC4417. The LTC4418 is specified over a commercial temperature range of 0°C to 70°C and an industrial temperature of −40°C to 85°C and is available in a 20-lead 4mm x 4mm QFN package.

Relevant LTC44 series products

Author：Brittany Antonia （The author of article owns the copyright.）