I've been using very low loss Schottky diodes (95SQ015 - Vf stays at
about 0.2v @ 1A last I checked)
QT

Ideal diode, such as LTC4358, would eliminate the voltage drop at the
cost of higher complexity.

Bart

First, a teaching moment for those non-techies about using diodes to
isolate two battery setups so that a bad battery won't suck the life
out of the good battery, see
http://aviation.derosaweb.net/presen...iring_2007.pdf
(page 21-25) for some explanations.

While I know about Schottky diodes and their low forward voltage drop
(0.2v which seems like the best of the diode worlds) but I had not
heard of the Ideal Diode which seems custom made for our application
of two battery sources and if one dies the other takes over. Good to
5A. What's not to like? But what is the critical forward voltage
drop? I read;

"The internal MOSFET turns on and the amplifier tries to regulate the
voltage drop across the IN and OUT connections to 25mV. If the load
current causes more than 25mV of drop, the MOSFET is driven fully on
and the voltage drop is equal to RDS(ON) x ILOAD."

25mv? GREAT NEWS!
RDS(ON) x ILOAD = 20milli-ohm x 5A = 0.1 volt. Better than a
Schottky. WHOOP!
(BTW: the small m for milli instead of big M for mega tripped me
up)

But then in the Specs Table I read;

ÄVSD Source-Drain Regulation Voltage (VIN - VOUT) 1mA IIN 100mA
l 25 mV (Typ)
ÄVSD Body Diode Forward Voltage Drop IIN = 5A, MOSFET Off l 0.8 V
(Typ)

So aren't we back to a silicon diode like forward drop? OK, when the
MOSFET is ON then we are back to the 0.1 volt. Interesting.

Lousy SM packaging for our application though. Bart - How are you
mounting it? Pictures?