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BQ35100: Ground System explanation

Max Dobbert
Prodigy 40 points
Part Number: BQ35100

Tool/software:

Dear TI-Team,

i want to use the BQ35100 for gauging an Li-SOCl2 Battery.
In Section "10 Layout" of the Datasheet of the BQ35100 under point "10.2.1 Ground System" is an ideal Ground System for the system Grounds explained.
It says the ground is separated into a low-current ground and and a high-current ground.

My questions are:

For what purpose is such a ground system used? / Is this system strictly necessary for accurate battery gauging with the BQ35100?

How would I implement the ground system if I have additional ICs in my design?

    - can components such as an DC/DC-Converter be connected to the low current-ground?

    - should the high-current ground exclusively be used for the load itself?

As always thanks in advance.

Kind regards,

Max Dobbert

  • 0
    TI__Mastermind 28480 points

    HI Max,

    The purpose of the two ground system is to allow for the sensitive components of the device to be separated and protected from the high current path that will be connected to the load.  If other IC's are in the design that are not directly connected to the high current path, I believe they can be included on the low current-ground. We recommend using the high current ground for the load and components that could access high currents, such as ESD Diodes.

    Regards,

    Anthony

  • 0 in reply to Anthony
    Prodigy 40 points

    Hello Anthony,

    thank you for the fast reply. 

    I do have a follow up question regarding the connection of the two ground paths.
    I want to connect the grounds with a 0 Ohm resistor. As I understand the datasheet, the connection should be placed close to the current sense resistor.

    My question would be:
    to which terminal of the sense resistor should I connect the ground connection?

    the datasheet of BQ35100 shows a connection between GND and BAT- (below picture)

    the EVM of the BQ35100 shows a connection between GND and PACK- (picture below)

    I do believe that the labeling in the datasheet is wrong and that I should connect GND and PACK- 

    What do you think?

    Regards,

    Max

  • +1 in reply to Max Dobbert
    TI__Mastermind 28480 points

    Hi Max,

    I believe that the 0 Ohm resistor should be places between GND and PACK- based on the EVM. 

    Regards.

    Anthony

  • 0 in reply to Anthony
    Prodigy 40 points

    Thank you very much!