Monolithic 18V Power Supply Priority Solution

Linear Technology Korea (CEO Hong Sa-gwak) has announced the launch of a dual-input monolithic power prioritizer (model: LTC4420) for 1.8V ~ 18V systems.

Electronic systems utilize batteries and capacitors as backup power supplies to enable portability, preserve memory during voltage sag (brownout), and ensure proper shutdown during power loss.


The LTC4420 typically supplies power from a primary power supply source such as an adapter or battery to the load and switches to a battery or expensive capacitor backup power supply during primary voltage sag or power loss.

Capable of operating up to 18V, the LTC4420 can handle various types of power sources including adapters, USB ports, supercapacitors, and lithium-ion, alkaline, or NiMH cell batteries. With a device operating current as low as 3.6µA and backup supply standby current consumption reduced to an extremely low level of 0.32μA, the LTC4420 extends operating time in portable battery-powered systems.

Unlike other solutions, the LTC4420 does not require the backup supply voltage to be lower than the primary supply voltage. When the backup supply voltage is higher than the primary supply voltage, the prioritizer becomes a better solution than a simple diode-OR. The prioritizer does not necessarily need to draw current from the highest voltage supply source. When the primary voltage drops below the adjustable switchover threshold, the internal 500mA (minimum) current-limit switch transitions from the primary power to the backup power supply.

To reduce standby current, the resistive voltage divider of the backup power supply is connected to a strobed ground with a duty cycle adjustable down to as low as 0.0015%, and an optional undervoltage shutdown function can prevent severe battery discharge. The Freshness seal mode within the IC lowers standby current to 0.12µA, minimizing battery discharge during product storage and shipping after production. Additionally, protection is provided against reverse battery voltages up to −15V being transmitted to the load.

The LTC4420 operates over a commercial temperature range of 0°C ~ 70°C and an industrial temperature range of −40°C ~ 85°C, and is offered in a thermally enhanced 12-pin MSOP and 3mm x 3mm DFN package. Pricing starts at $2.95 per unit in quantities of 1,000 units. Device samples and evaluation kit boards are available for purchase through online channels and regional sales offices.