why two regulators on Mega board?

On the schematic, shows wired in parallel:
MC33269ST-5.0T3
MC33269D-5.0

And both parts seem to be mounted on my Mega board... both spots occupied, one regulator is smaller package than the other. I'm not used to seeing linear regulators ganged up like this. It just seems odd.

Is there some benefit for two regulator off the other for handling transient response, or is this just to offer up a little more current for loads?

I don't think both regulators would have the exact same Vout, what's the effect of that?

For example, if one is trying hard to supply say 5.1 volts until it maxes out and starts to sag under its full load... where it falls back and the other sitting at Vout = 5.0 starts to contribute.

It's an alternate part choice. The component you think is the 2nd regulator is the power transistor for the automatic power switching.

DOh! I'll put on the glasses and look at little harder at the numbers mounted on the board next time.

thx

That one threw me also when I came across it some time back. I had never seen a 'alternate part' actually drawn into a schematic before, usually it would show up as just a note below the drawing giving alternate part numbers, or would just be shown in a part listing drawing.

Lefty

I had never seen a 'alternate part' actually drawn into a schematic before

In this case, it permits two sets of pads to be put on the PCB, so that either part can be mounted despite the fact that the have different packages (I believe the PCB actually has the packages overlapping, so that it would be impossible to include both.)

Well, the transistor that switches power sources is similarly shown on the schematic.. two different part numbers wired in parallel.

Probably following the same kind of logic as the alternate parts for regulator.

Well I dont seee two MOSFETS on the schematic but I do see two opamps

but I do see two opamps

Those two opamps are inside a single 8 pin package.

Lefty