The LT4351 creates a near-ideal diode using external
single or back-to-back N-channel MOSFETs. This ideal
diode function permits low loss ORing of multiple power
sources. Power sources can easily be ORed together to
increase total system power and reliability with minimal
effect on supply voltage or efficiency. Disparate power
supplies can be efficiently ORed together.
The IC monitors the input supply with respect to the load
and turns on the MOSFET(s) when the input supply is
higher. If the MOSFET’s RDS(ON) is sufficiently small, the
LT4351 will regulate the voltage across the MOSFET(s) to
15mV. A STATUS pin indicates the MOSFET on state.
An internal boost regulator generates the MOSFET gate
drive voltage. Low operating voltage allows for OR’ing of
supplies as low as 1.2V.
The LT4351 will disable power passage during undervoltage
or overvoltage conditions. These voltages are set by
resistive dividers on the UV and OV pins. The undervoltage
threshold has user programmable hysteresis. Overvoltage
detection is filtered to reduce false triggering.
The LT4351 is available in a 10-pin MSOP.