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BQ40Z50-R1: SMBUS questions

Ann_Lien
Genius 14430 points
Part Number: BQ40Z50-R1

Hi expert,

Customer is asking for several questions on bq40z50-R1 shown below. Would you kindly help to answer Q3 and verify if my comment is okay? Thanks a lot!!

  1. What will happen to the SMBus when the battery is fully discharged causing the FETs to open up?
  2. Do they still work or pull low to GND?
  3. Can you communicate with EC sending CC and CV commands?
  4. When the FETs open up, does that mean it entered shutdown mode?

My comment:

For Q1: Gauge IC will sense DATA/CLK are low and goes into sleep mode. So it will get into sleep mode.

For Q2: Communication would be not able when two lines are pulled to GND.

For Q4: When VPACK is lower than 2V typ., then FET will open and it would enter shutdown mode.

Best regards,

Ann Lien

  • 0
    TI__Guru* 76230 points
    Hi Ann
    1. If the cell is fully discharge and yet you have the host communicating with the gauge, the gauge will still remain accessible
    2. The lines will still work.
    3. What do you mean by EC? The gauge WIll still be accessible by your host.
    4 No. the voltage has to go below shutdown voltage for the device to be shut down

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Genius 14430 points
    Hi Onyx,

    Thanks for your reply!!
    For Ans #1 and #2, we need to make sure SMBus is pulled high, right? If there is no pull-up source then SMBus will be disabled.
    For Q3, EC means NB Embed Controller which is host to control all signal in NB. You can consider it is a host.
    For Q4, shutdown voltage is 2V, right? So when voltage is lower than 2V typ., it will enter shutdown mode.

    Add one more question on sleep mode, how can we get exit sleep mode? Thanks a lot!!

    Best regards,
    Ann Lien
  • 0 in reply to Ann_Lien
    TI__Guru* 76230 points

    Q1,Q2. Yes without a pull up, comm will be disabled.

    Q3. yes. With BCAST enabled. See section 4.11 of TRM

    Q4. There are other conditions to enter shutdown. See section 5.4 of TRM

    Q5. See the conditions to exit sleep mode in section 5.3 of TRM

    Link to TRM below:

    http://www.ti.com/lit/ug/sluubk0b/sluubk0b.pdf

    thanks

    Onyx