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2 pc of LT3012 paralleled together (but no need for load sharing)

I have an application, that consist of 2 boards:
 - "MCU-Board" (powered by USB or by the "Base-Board")
 - "Base-Board" (powered by 12V or by the "MCU-Bord")

In normal operation this boards are plugged together, and powered by 12V (automotive).

my Idea was to use two LT3012 and make use of the built-in "reverse current protection" of this part.

# When the boards are sparated, both boards have to run on its own.

# Can I plug the boards together (3,3V/GND) without using any additional diode or switching logic ? (by using the built in "reverse current protection" of the LT3012)

# When plugged together both(!) boards have to run from the "5V-USB" only OR from the "12V-automotive" only OR even both(!) of this supplies connected.

# there is no need for load-sharing

Is it "allowed"/possible to simply connect the two outputs of the two LT3012 together in the described way ?

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  • >>"Can you use the approach using the LT3042 that I show in the image below?"
    unfortunately I need the wide input voltage range of the LT3012 (4...80V)

    If I understand you right the stability Problem does occur only at the time when both LDO's are powered ?

    looking again on my picture:  ...

    would it do the trick / enhance the stability
    if I trim e.g. the 12V LDO to 3.4V and the other (5V/USB-) LDO to 3.2V
    and then
    when both LDO's are powered only the 12V LDO [3.4V] delivers current ?
    (cause the other (5V/USB-) LDO [3.2V] can not act as a sink because of its reverse current protection ?)