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INA282 High current draw

Eric Hajduk
Prodigy 20 points
Other Parts Discussed in Thread: INA282

We are using the INA282AIDR current sensor in an application where we measure  current draw from a 30V battery on the high side.

We have been using the sensor in our design for about 1 year and it has been functioning as expected. We have currently had a number of cases where the circuit has drawn excessive power and triggered shut down procedures.

The current measuring circuit functions such that the power to the INA282 is turned on and off to conserve power. The datasheets specify that the INA282 can be used in this format.

The failure rate we are getting is about 5%. We have traced the source of the excess power to the INA282 through the sense pins. We traced the lot codes of the INA282 that are failing to

  •         AQDJ G4     -  15 failures
  •         C16P G4      - 7 failures

Where the previous lot in our production 'AQDK G4' functioned fine.

We are not sure if our design is such that we are on the edge for how we are using the INA282, or if something has changed in the manufacturing process of the INA282.

Please respond with any questions as we need to resume production.

Below is the circuit.

 

  • 0
    TI__Genius 14825 points
    Eric,

    This is troublesome indeed. I wasn't able to see your circuit - could you try attaching it as a file?

    There aren't any fab changes that I'm aware of, but I will have someone run those lot codes and see if something happened.

    What kind of current do you consider excessive? The inputs should sink tens of uA I believe, but if you are seeing more, then perhaps something is getting damaged? Perhaps you are, as you said, on the edge with your design?

    One thing to note - it is a holiday weekend here so people will mostly be returning to work next Tuesday. We'll support you as best we can through the weekend but on some things our hands may be tied, and I do apologize for that in advance.
  • 0
    Prodigy 20 points

    Hi Jason,

    Thanks for your help in dealing with this.


    Attached is a screen shot of the schematic.
    As for current levels, what we are seeing is one or both of the 50mA surface mount fuses that are in the sense pin blow. We would normally expect the current to be in the microamp range. We place these 2  fuses in the sensing arms because we measure current on the high side (typically 40V max). Once the device is inspected if we replace the blown 50mA fuse(s) it works normally.

    Since my post to the forum, we ran some tests where we replaced the 2, 50mA fuses with 0 ohm resistors and added a 62mA axial fuse on the ground line of the total circuit. The 62mA fuse is much higher than what our circuit normally peaks at (12mA).
     What we have seen on one unit so far, is that the  62mA fuse being blown. In this case when we looked at the unit the INA282 was drawing about 80mA continuously, it was damaged in some sense.
    One note, from our experience the surface mount fuses are much quicker blowing compared to the axial fuse.



    Thanks
    Eric

  • 0 in reply to Eric Hajduk
    TI__Expert 5705 points

    Hello Eric,

    These types of unexpected or unpredictable behaviors can occur when the conditions specified in the "absolute maximum ratings" section are violated. So before we start digging into any process changes I would like to eliminate this possibility. Could you please post a scope-shot showing REF2 and V+ (or POWI) as the INA282 is powering up? Thank you.

    Best Regards,
    Harsha Munikoti