• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 31 subscribers
  • Views 788 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8850: Current leakage on VPROPI

Chuchen Wang
Expert 3470 points
Part Number: DRV8850

Hi,

My customer is conducting failure analysis on a unit of their product that is about to go into production.  They see a small amount of current leakage on VPROPI of the motor driver (DRV8850) when enabling the motor but without any motor movement.
 
The following scope traces shows the motor enable signal (MTR_EN) going high and the current leakage (ADC_MTR_I - this is VPROPI output) at around ~20mV (~122mA):

This event only occurs during reverse direction and not during forward. Furthermore, we used a different board to test this and found no leakage current in either direction:

 
We have the a few questions we are hoping to get answers as soon as possible:
1. What is contributing to the different current reading between forward and reverse when motor is enabled?( Are there 2 sets of current measure circuitry, one used for forward and the other used for reverse? or Its the same circuitry but with forward and reverse current going through different path? )
2. Is Iout valid when motor is disabled? or Iout is valid only when motor is enabled?
3. What is the accuracy of Iout at low motor current condition?
4. What is the TI's manufacturing defect rate for this IC?

Thanks,

Chuchen

  • 0
    TI__Guru** 114905 points
    HI Chuchen,

    "My customer is conducting failure analysis on a unit of their product that is about to go into production." Did only one device act this way? How many did not fail?

    1. What is contributing to the different current reading between forward and reverse when motor is enabled?( Are there 2 sets of current measure circuitry, one used for forward and the other used for reverse? or Its the same circuitry but with forward and reverse current going through different path? )

    There are two separate circuits.

    2. Is Iout valid when motor is disabled? or Iout is valid only when motor is enabled?

    Iout is not valid when the motor is disabled.

    3. What is the accuracy of Iout at low motor current condition?

    What is low motor current?

    4. What is the TI's manufacturing defect rate for this IC?

    This information is not disclosed. The devices are tested for proper operation prior to shipping.
  • 0 in reply to Rick Duncan
    Prodigy 80 points

    Hi Rick,

    For your question on how many have fail: At the moment 1 out of 500 have been identified. We don't generally check for this issue so it might be present in other units at lesser degree which might not interfere with the normal operation of our system. In this unit, it was significant enough to make it to failure analysis.

    For your responses:

    1. Can you provide more info on the two separate circuits that measure current (forward and reverse)?

    2. Thanks for your answer here

    3. Low motor current for our application is between 100 to 300mA. Can you provide accuracy information at those levels and at lower or higher levels? Is there accuracy graph or info we can take a look at?

    4. If the expectation is for devices to be fully operational at shipping. What conditions could affect the device to have this behavior?

    Thanks,

    Martha Calderon

    Electrical Engineer, Synapse Product Development

  • 0 in reply to Martha Calderon
    TI__Guru** 114905 points
    Hi Martha,

    1. Can you provide more info on the two separate circuits that measure current (forward and reverse)?

    The circuits are similar. The difference is the path of the current. In the forward direction, the current is monitored through the high side FET of OUT1. In the reverse direction, the current is monitored through the high side FET of OUT2.


    3. Low motor current for our application is between 100 to 300mA. Can you provide accuracy information at those levels and at lower or higher levels? Is there accuracy graph or info we can take a look at?

    I could not find accuracy information on those levels. If you are trying to measure 100mA, have you considered measuring the VPROPI with no current and subtracting any offset?

    4. If the expectation is for devices to be fully operational at shipping. What conditions could affect the device to have this behavior?

    It is difficult to speculate. Have you monitored through the system to ensure there is no unexpected current?
  • 0 in reply to Rick Duncan
    TI__Guru** 114905 points
    Hi Martha,

    I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out)