LT3080 SET TO OUT ABS. MAX. IN OVERLOAD

Field support asked a good question so I will post it here:

Question:  Won't the OUT to SET abs. max. rating be violated if OUT of the LT3080 is in overload, since SET will program one voltage but the overloaded OUT will be a lower voltage?  For example, start up into a very large output capacitor may cause the LT3080 to go into overload until the large output capacitor is charged.   I show the abs. max. rating from the LT3080 datasheet in the image below:

LT3080 DS abs max_1.png

  • +1
    •  Analog Employees 
    on Nov 26, 2019 6:12 PM over 1 year ago

    Note 7 of the LT3080 datasheet says that OUT and SET are clamped to each other with diodes.  I show Note 7 in the image below.  If OUT of the LT3080 is in overload and cannot regulate voltage, OUT will pull down SET because of the clamp diodes.  I show that behavior below in a scope capture of an overload condition.  I also show the schematic.  Except for extreme conditions like a large CSET and a fast overload dv/dt, the OUT to SET current will not be enough to violate the OUT to SET abs. max. rating. 

    LT3080 DS Note 7_1.png

    CONDITIONS:  LT3080EDD, DC995A, 2.5VIN, 5VCTRL, OVERLOAD into 1 Ohm to 500mOhm to 1Ohm, VSET VOUT IOUT_0.bmp

    LT3080EDD, DC995A, 2.5VIN, 5VCTRL, OVERLOAD into 1 Ohm to 500mOhm to 1Ohm, VSET VOUT IOUT_0.bmp

    11-26-2019_9-17-31.jpg