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LM7481-Q1: LM74810 system quiescent current abnormal

Michael Huang
Prodigy 160 points
Part Number: LM7481-Q1

Hi TI expert,

In our ADAS project, we use two LM74810 chips as ORing reverse protection circuit.

Now we met a case:  Normally, our controller quiescent  current is lower than 1.5mA(limit for 25℃), now one controller quiescent  current is 4.5mA. By analysis, over limit is caused by LM74810

in backup VBAT(S11006 in schematic below), and by ABA change confirmed this cause. This LM74810 system quiescent current is abnormal! Do you meet similar issue before?

As this issue is detected in production line, is it possible a chip quality problem?

...

Thanks!

Michael.Huang

 

  • 0 in reply to Michael Huang
    TI__Guru 57737 points

    Hi Michael,

    Thanks for reaching out to us. Please share the information requested below,

    1. The schematic shared is not readable. Please share it in PDF format as attachment. 
    2.  The maximum quiescent current (IC GND current) of LM74810-Q1 is only 480uA. Can you let us know how you have tested/ measured the quiescent current of the IC.  
    3. I can see that there are 2x LM74810-Q1 in ORing configuration. While measuring the quiescent current of one LM74810-Q1 is the other LM74810-Q1 input powered or is it floating ?
  • 0 in reply to Praveen GD
    Prodigy 160 points

    Hi Praveen,

    1. The schematic shared is not readable. Please share it in PDF format as attachment. Attached.
    2.  The maximum quiescent current (IC GND current) of LM74810-Q1 is only 480uA. Can you let us know how you have tested/ measured the quiescent current of the IC.  
      1. We had done the ABA change experiment, when bad LM74810 soldered on normal board, sleep current is over limit; when good LM74810 soldered on abnormal board, sleep current is normal.
    3. I can see that there are 2x LM74810-Q1 in ORing configuration. While measuring the quiescent current of one LM74810-Q1 is the other LM74810-Q1 input powered or is it floating ?Both LM74810 are powered and enable, you could check the attached schematic.VBAT_Reverse.pdf
  • 0 in reply to Michael Huang
    TI__Guru 57737 points

    Hi Michael,

    1. The schematic looks good to me.

    2. The quiescent current of the LM74810-Q1 is the current that is measured coming out of the IC GND pin. Looks like you are measuring the input power path current when the board is in low power/Sleep mode. This is not equal to the LM74810-Q1 quiescent current  as there can be multiple current paths in the circuit other than the current drawn by the LM74810-Q1. Unless you measure the current flowing out of the IC GND pin we cannot be 10)% sure if the excess current dawn in the board is taken by LM74810-Q1.

    3. On how many boards out of how many total boards  do you see excess input current being drawn in sleep mode.

    4. Is there any test performed before measuring the input current that can damage the LM74810-Q1 IC ?

     

  • 0 in reply to Praveen GD
    Prodigy 160 points

    Hi Praveen,

    2. The quiescent current of the LM74810-Q1 is the current that is measured coming out of the IC GND pin. Looks like you are measuring the input power path current when the board is in low power/Sleep mode. This is not equal to the LM74810-Q1 quiescent current  as there can be multiple current paths in the circuit other than the current drawn by the LM74810-Q1. Unless you measure the current flowing out of the IC GND pin we cannot be 10)% sure if the excess current dawn in the board is taken by LM74810-Q1.

    A:For current two confirmed boards, ABA exchange experiments show that current over limit is caused by LM74810: solder the suspected 74810 on good board 

    sleep current is abnormal. solder good 74810 on abnormal board, sleep current is abnormal, abnormal issue goes with 74810 chip.

    3. On how many boards out of how many total boards  do you see excess input current being drawn in sleep mode.

    A: Currently confirmed boards caused by LM74810 is 2 in 20+ boards.

    4. Is there any test performed before measuring the input current that can damage the LM74810-Q1 IC ?

    A: No test performed, it's detected in production line.

     

    Thanks!

    Michael.

  • 0 in reply to Michael Huang
    TI__Guru 57737 points

    Hi Michael,

    We can measure the device quiescent current from our side on ATE and confirm if it is within limits. Please reach out to our field applications engineer and submit the failed samples for Failure Analysis. 

  • 0 in reply to Praveen GD
    Prodigy 160 points

    Hi Preveen,

     We have reached FAE and following analysis is on going.

    Thanks!

    Michael.Huang