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TPS7A4701 and TPS7A3301 mutual shutdown

Other Parts Discussed in Thread: TPS7A47, TPS7A33

Hello dear Ti.

I need to ask few question regarding those LDO's.
I'm using them both in my dual PSU:

#1 should I use clamping diodes on outputs? Because they do not start at the same time (TPS7A3301 is faster as I remember),
#2 is it safe to place a capacitor between V+ and V- rail (rail-to-rail decoupling)?
#3 according to schematic below (from D. Self book) those mutual shutdown circuit will work with those regs? If yes do they suffer any performance drop due to non common cirucit?
#4 some time ago I saw some PDF (from Ti site) which mentioned about adding some diode connected to FB pin, could you remind me what for? I couldn't find that paper ATM.

  • Hi Mateusz,

    1) I would advise adding the diodes to mitigate any potential problems. It's easier to not populate a part on a board then to revise the board.
    2) I would advise against this
    3) The enable pins on the TPS7A47 and TPS7A33 can be tied together, so long as the TPS7A33 enable voltage does not go above 10V. This should be an easier way to get mutual shutdown.
    4) The paper you mention was on the pros and cons of using a feedforward capacitor with an LDO. For larger feedforward capacitors we do recommend placing the advised diode (generally Cffs much larger then 100 nF). Article here:
    www.ti.com/.../sbva042.pdf

    Regards,
    David