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BQ27441-G1: Hardware integration practice for BQ27441-G1 in production

Andrew Ameri1
Prodigy 20 points
Part Number: BQ27441-G1
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hi,

I'd like to use BQ27441-G1 in a system where I have multiple I2C devices on the same bus as this fuel gauge connected to a host micro-controller. I have a few questions regarding correct practice of hardware implementation when it comes to high volume manufacturing:

1- I understand we can configure the fuel gauge using BQStudio. What's the correct practice for providing flexibility of using BQStudio in my schematics? Should I just simply put pin-headers for tapping into I2C line and connect EV2400 externally using jumper wires? Is BQStudio used in production stage or there's a work-around using host micro-controller? 

2- A LiPo battery is permanently connected to the system and because of the nature of our design the load cannot be disconnected from the fuel gauge. How can we perform the board offset calibration properly? There's indeed a power button in the system but there are other components before the switch which doesn't let the current flow through BQ27441-G1 sense resistor to be absolute zero. In prototyping stage there's definitely a work around for this to disconnect the load (i.e. using jumper). However, I was wondering if we can bypass this stage in production by using same board offset calibration value from prototyping stage. 

3- Since the fuel gauge already has temperature readings, we would like to use that data in other part of our software logic for different purpose. Does BQ27441-G1 do the temperature measurement using the 10k pulled-down resistor (thermistor) connected to pin BIN? Or it has its own internal temperature sensor? 

Note: We are planning to permanently pull down pin BIN since the battery is embedded in the device.

Thanks,

  • 0
    TI__Guru 52115 points
    See my comments below.
    1.  Once you finalize your gold image, you can generate a gm.fs file in the Golden Image tab of bqStudio. You can use your micro-controller to program the gm.fs file to the bq27441-g1 device. See the details in the app note below.
    1. Allow me to check internally.
    1. The battery pack thermistor can be connected to the BIN pin. Also, bq27441-g1 has an internal temperature sensor.

    Andy

  • 0 in reply to Andy Liu (BMS)
    TI__Guru 60916 points

    About #2, board offset: It's very uncommon to have a fixed DC board offset (i.e. a voltage that is in addition to the voltage over the sense resistor). So this is usually not calibrated. Make sure that the sense resistor uses a kelvin connection and keep the traces between SRx and the sense resistor as short as possible.

    If for some reason your design adds a fixed DC voltage and that is the same for every unit, you can perform a board offset calibration for one board and use the results in the golden image (.gm.fs) when you configure the gauge.

    Configuring the gauge: Please only configure the gauge when ITPOR = 1. The algorithm is adaptive and every time you configure the gauge, the algorithm loses whatever it learned. It would be a mistake to configure the gauge when it wasn't reset (ITPOR = 0).