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DRV8711 Register 1 Bit 10 Issues

ErnestHanks_55
Intellectual 460 points
Other Parts Discussed in Thread: DRV8711, DRV8711EVM

Hello TI,

We are having an issue with our DRV8711 Register 0x01 Bit 10. This is very bad for us since I'm planning on using the Internal Stall Detect feature. *NOTE: Bit 10, not Bit 11* (I am aware Bit11 is a reserved bit and it is to be masked out)

 

In the Right-Hand-Side screenshot (Top is WRITE-REGISTER, bottom is READ-REGISTER), you will see confirmation that our Register-Write and Register-Read appears to work properly for every other register.

-The top screenshot shows a REGISTER-WRITE configuring all registers in the chip.
-The bottom screenshows a REGISTER-READ reading all the registers.

You will notice that all values are read back as expected, with the exception of Register 0x01 Bit 10. We are unable to change this Bit regardless of what value we try to write.

We have seen this on every board and every chip thus far (qty=8 chips).

  • 0
    Intellectual 460 points

    Sorry forgot to add waveform. See attached.

    I should also add that I've confirmed the SPI write into Bits [11:0] are working all properly in ALL other registers ex cept register 1.

  • 0 in reply to ErnestHanks_55
    TI__Expert 4650 points
    Hi Ernest,

    We have not seen this behavior before. I will test on our side and get back to you. A couple questions for my debug:

    1.) What is the state of SLEEPn during this testing?
    2.) What is the VM Voltage?
  • 0 in reply to Phil Beard
    TI__Expert 4650 points
    Also, just to confirm, are you able to see changes in bits 8 and 9 between read and write functions?

    If the device is reset does this register come up as the proper default value?
  • 0 in reply to Phil Beard
    Intellectual 460 points
    1) Whether SLEEPn=0 or SLEEPn=1 makes no difference, I tested both.

    2) Vm=24 V. In regards to the general "is stuff working...", yes it is. This design is fairly far along. We have been running motors for several months now meaning configuration, different motors, etc. I only caught this issue when I tried to start implementing the Integrated Stall Detection (which I had running on the DRV8711EVM before this design started).

    3) Yes bits 8/9 are changed correctly. So into SMPLTH I can write 000, 001, 010, 011 no problem, but then any attempt to change bit 10 does nothing. So writing 100 reads as 000, 101 reads 001, 110 reads 010, and 111 reads 011. So bit 10 is the only bit.

    4) I will have to get my FW engineer to check this. I'll get back to you soon.
  • 0 in reply to ErnestHanks_55
    TI__Expert 4650 points
    Hi Ernest,

    It was brought to my attention that this is a documented error on our part. There is currently a change request being processed for the datasheet.

    The bit is properly written and the back EMF threshold will change, but the read back is incorrect. Our suggested solution is documented in this post:

    e2e.ti.com/.../317413

    We apologize for the confusion with this part.
  • 0 in reply to Phil Beard
    Intellectual 460 points
    Great! This should be put in some sort of errata or documentation.

    I tried scanning the E2E forums but guess I missed that post.

    Thanks so much huge time saver.