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LT1764 Ioff

Tom Roe1
Prodigy 90 points

I am thinking about using the LT1764 in a new product. I would like the shut down pin, when active, to open up the output but I am not sure what it does, I can't find it in the DS. I mostly need to know if current from the load will flow into the out pin when it is shut down, and how much.  Maybe there is a LDO that has Ioff specified?  I would need about a 0.5 Amp 3.3V output  from a 5V input.  -40 to +85 Temp.

Thanks Tom

  • 0
    TI__Expert 5555 points

    Hi Tom,

    Are you sure this is a TI device? I think this might belong to Linear Tech.

    I can't speak for their device but traditionally a shutdown pin is similar to an enable pin in that it dictates whether or not there is a regulated voltage at the output. 

    We could always assist with an LDO in the TI portfolio.

    Let me know if you need any help,

    Aaron

  • 0 in reply to Aaron Paxton
    Prodigy 90 points

    Sorry about that. I would like a TI part. I need a LDO that is:

    5V in but can handle 12V transients.

    3.3V out at 1A. Can be adjustable Vout.

    Tj = 125, -40 to 85 operation.

    Needs to shut off to the output and allow very little current to come back from the load when off.

    Typical dissipation is about .5W

    Thanks

    Tom

  • 0 in reply to Tom Roe1
    TI__Expert 5555 points

    Tom,

    TPS7A4701 is a good cross here. Are you worried about noise on your power rail?

    As for the current from the load, could you describe where this current could be coming from? I'm presuming you mean from a capacitor that is discharging but would like to get more detail.

    Basically, when you disable (or shutdown) the LDO, you are effectively disabling the internal FET. As a result, your LDO output will become grounded. Any charge from an output cap will dissipate through the resistor divider and load. 

    Also, if you could provide a schematic, that would also be very helpful. 

    Thanks,

    Aaron