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Reverse Output Current through a LT3045

Category: Hardware
Product Number: LT3045
Software Version: N.A.

Hello,

I would like to use the output of an LT3045 LDO (set at +5V in this case) as the upper voltage rail for a protection diode as pictured below:

At an input voltage around 5.7V (on the TRIG-SYNC In line) the diode begins to turn on (1 mA current), and at an input voltage of 6.0V the diode is at it's maximum current (200 mA).

My question is, in the broadest terms, will this work?

Particularly, how much reverse current will the LT3045 output tolerate and where does that current go?

Thank you very much for your help,

Tony

Top Replies

  • Hello Tony,

    Particularly, how much reverse current will the LT3045 output tolerate and where does that current go?

    my answer for a standard LDO would be: "it will not work, the LDO output can…

  • Hi,

    To supplement 's spot-on advice:

    If the TRIG-SYNC comes from an external (unknown) source, it may be preferable to use a comparator instead of a logic gate as the front-end. If the input…

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  • Hi,

    To supplement 's spot-on advice:

    If the TRIG-SYNC comes from an external (unknown) source, it may be preferable to use a comparator instead of a logic gate as the front-end. If the input signal hovers halfway the supply voltage, the input stage of the logic gate will draw considerable current from the supply. A comparator won't have that problem. That is, have a comparator together with a voltage divider at the input, with some positive feedback (for hysteresis). Place the diode protection circuit to that comparator input  (You want to put the protection circuit behind some series resistance in order to limit the clamp current).

    Cheers,

    heke, AsamaLab

  • Hello Heke,

    Thank you too for you answer.

    What you suggest is correct and will work, but I'm not too concerned about the user putting a DC-ish, or very slow edge voltage at around 2.5V. The input is labeled for a LVTTL trigger and they should understand that.

    Also the buffer I'm using has Shcmitt trigger inputs. I understand this does not eliminate the high current problem at mid-voltage, but at least it eliminates the possibility of oscillation around that point. So it solves half the problem, and I'm ok with that.

    Thank you again and best regards,

    Tony

Reply
  • Hello Heke,

    Thank you too for you answer.

    What you suggest is correct and will work, but I'm not too concerned about the user putting a DC-ish, or very slow edge voltage at around 2.5V. The input is labeled for a LVTTL trigger and they should understand that.

    Also the buffer I'm using has Shcmitt trigger inputs. I understand this does not eliminate the high current problem at mid-voltage, but at least it eliminates the possibility of oscillation around that point. So it solves half the problem, and I'm ok with that.

    Thank you again and best regards,

    Tony

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