PowerPath™ prioritizers are low operating current circuits that provide backup switchover power for keeping critical circuitry alive during brownout and power loss conditions based on a user-defined priority. Priority is defined by pin assignment, with V1 assigned the highest priority and V3 the lowest priority. This is in contrast to discrete OR'ing diodes or ideal diode PowerPath Controllers that give priority to the supply with the highest voltage. Some ideal diode devices can be used as prioritizers, but the solution requires higher power, more external components, and additional board space. Our family of prioritizers is highlighted, with key features and benefits of each product discussed.
The LTC4417 uses external P-channel MOSFETs and connects one of three valid power supplies to a common output based on priority. Two or more LTC4417s can be cascaded to provide switchover between more than three inputs.
The LTC4419 and LTC4420 are dual input monolithic prioritizers with an internal 2Ω, 500mA P-channel MOSFET. The LTC4420 disconnects the secondary power source when main power has been removed and the monitored secondary source voltage falls below a user-defined threshold.