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BQ34Z100-G1: Is BAT- connected to two grounds

Mohamed Smaili
Prodigy 20 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100

Tool/software:

Hello TI Support Team,

In the datasheet for BQ34Z100 BQ34Z100 datasheet  AGND and GND are connected together near BAT- as depicted in the picture above. I know that  the reason this is done is to help prevent noise from the power trace's GND from disturbing the signal level grounds. My question is should we connect the two grounds directly or from my knowledge I know that its better to add a small low pass filter such as a capacitor or a ferrite bead between the two grounds ? And if I should add a low pass filter capacitor what is my cut off frequency suggested in order to calculate the value of the capacitance of the capacitor ?

  • +1
    TI__Mastermind 25475 points

    Hello Mohamed,

    The ground between the IC and the cell should stick together and not be interrupted due to the IC using that ground within its voltage referencing. there is no need to attach a low pass filter as long as you follow the example schematics in the datasheet and the EVM. 

    Thank you,
    Alan

  • +1 in reply to Alan Frias
    Prodigy 20 points

    Hello Alan, 

    Thanks for your answer, 
    A small question we can see that the BAT- is connected to both the AGND and DGND stated as GND, same applies to the IC there are some of its components connected to the GND and the IC it self through Vss is connected to AGND, that was my question since the IC is using both ground shouldn't we filter out the ground through a low pass filter ?
    Also it is mentioned in the layout section of the datasheet of the IC that the two grounds are connected on the blue point and it seems like a small capacitor ?

    Appreciate your help again, waiting for your clarification. 

  • +1 in reply to Mohamed Smaili
    TI__Mastermind 25475 points

    Hello Mohamed,

    No low pass filter is need on the ground and AGND and GND are the same netlabel. 

    Thank you,
    Alan