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BQ35100: Regarding EOS mode and GE Enable pin

Sim Hau
Prodigy 50 points
Part Number: BQ35100

Dear Sir,

1. Is there an interrupt pin to MCU, to trigger when BQ35100 sense/realize it is in EOS mode? Or the communication will go via I2C? The main reason we are asking because we want to save power so we do not want to always get the MCU to pull the I2C message. At least, when BQ35100 realized the LiSoCl2 battery is almost flat. 

2. From the data sheet, look like the MCU need to control the GE enable pin in order to save the overall power. By default, if we are using LiSoCl2 primary battery, how long or how many times that BQ35100 need to wake up to read in order to catch the Battery is in EOS mode? My concern is, for example, if we only enable the IC for every 1 hours, is there any possible that the battery get EOS/Flat/Empty before the system receive the EOS message?

3. For our design, we are using TL-5930, LiSoCl2 primary battery, 3.6V with 19Ah capacity. Our system standby current is currently measured at 0.11mA. Our radio will be turned on approx 4 times a day, and during the transmission, the peak current can go up-to 220mA. With the simple circuity from the BQ35100 datasheet, with the sensing resistor value of 0.1oHm, not sure whether it can be apply to our design?

4. Can we use BQ35100 to show indicate the remaining battery capacity? Eg, 100%, 80%, 60% .... 0%, to let user know the remaining capacity, and when the system receive the EOS message, then we can alert user to replace the battery. Again, we are using TL-5930, LiSoCl2 primary battery, 3.6V with 19Ah capacity.

Thanks.

From

Sim

  • 0
    TI__Guru* 76230 points
    Hi Sim,
    1. There is an alert pin.
    2. This will depend on how long your application is expected last. Closer to the time period when the application is expected to die, you can start taking more frequent measurements.
    3. This device was designed for such applications. Ps see the EVM user guide reference schematic.
    4. If the chem id used is a match for your cell, then the SOH prediction will be good. You determine cell match by nomenclature

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 50 points
    Hi Onyx,

    1. Per my understanding from the datasheet, the alert pin is on trigger when we go below the voltage threshold that we set. So is it saying that, this pin also been use, if the IC detect the battery is EOS (For Li-SOCL2) & SOH (For Li-MnO2), the trigger the MCU via the ALERT pin? Also, IF the IC GE pin is not enable, will the ALERT pin work?
    2. This is a good idea, but can you provide more information how can we determine whether the battery is lean towards the EOS stage? Example, what's the information from the BQ35100, so that we can get MCU to trigger more often on the GE enable pin?
    3. Yes, we are referring the EVM reference schematic for our schematic. There is a concern raise from our side, as the sensing resister from the reference schematic, section 4.1 of the document(sluubh7.pdf), show 0.1Ohm. That's why, we are asking whether it can sense our standby current of 0.11mA?
    4. Unfortunately, we are using Li-SOCL2 battery type not LiMnO2. So besides EOS, is there a way we can indicate user the remaining battery capacity?

    Thanks.

    From
    Sim
  • 0 in reply to Sim Hau
    TI__Guru* 76230 points
    1. GE pin has to be enabled.
    2. You experimentally determine this by testing your battery to understand it's aging profile.
    3 In accumualtor mode, the resolution which the gauge can report is 1mA. To report higher currents you will have to scale the current measurement referencing the app note.
    www.ti.com/.../slua792
    4. If you use the gauge in accumulator mode, your host can calculate the SOH based on the data from the gauge. If you use in EOS mode, the cell has to be characterized by TI if a chem id does not exist for the cell for the gauge to report SOH relatively accurately based on the resistance profile.
  • 0 in reply to Onyx Ahiakwo
    Prodigy 50 points
    Hi Onyx,

    1) So base of on previous item 3 and 4, if I am using Li-SoCL2 battery, with BQ35100, I can only detect whether it is EOS mode or not. For Li-SoCL2, there is no way to indicate the remaining percentage of the battery capacity right?
    2) For the question to know the EOS of the battery, the test I can do is to let it run until the battery dead, but with this, is there a parameters that I can read by from BQ35100 via I2C to our MCU, to determine the battery is going EOS?

    Sorry that, I am trying to ask more specific questions, as we are short of time as we need to gerber release the board, so we need to ensure the BQ35100 that we design in is working per our expectation.

    Thanks.

    From
    Sim
  • 0 in reply to Sim Hau
    TI__Guru* 76230 points
    Hi Sim
    1.There is if the chem id is an exact match for the cell. The gauge will report SOH via resistance-SOH correlation
    2. There are flags that get set when the gauge determines the cell is at EOS. Ps see the Technical reference manual for additional details.

    www.ti.com/.../sluubh1

    thanks
    Onyx