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BQ24707A: Where to connect the ground, it confuses me.

user4012620
Prodigy 30 points
Part Number: BQ24707A

Hello,

It may be a simple and difficult question, but where should I connect the bq24707A IC Grand?

・Battery negative terminal according to Simplified Schematic. That is, P_GND?

・According to a typical schematic, the adapter and the negative terminal of the battery. In other words, P_GND?

・According to the Pin Function, GND is described as being connected to the analog plane. 

I designed the board by connecting it to the signal GND, but the noise synchronized with the switching of the MOSFET overlaps the SMBus.

Is it still the correct way to connect to the signal GND?

Thank you.

Regards,
Shinya T.

  • 0
    TI__Mastermind 24075 points

    Hi Shinya,

       Usually these boards are designed to be 4 layer with 2 ground planes, an analog ground and a power ground. The power ground is the reference to PGND and all the high current carrying/switching circuitry ground reference should be connected to PGND. The analog sensitive pins should be connected to AGND so that switching noise does not couple on to the ground reference of the analog sensitive components. The AGND and PGND should be connected with a net tie or 0ohm connection close to IC.

  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Hello Kedar Manishankar,

    Thank you for your reply.
    In this case, I understand that the GND pin should be connected to the Analog ground plane.
    As described in Pin Functions, should the Analog ground plane and Power ground plane be connected only by the via provided under the Power PAD?

    Best Regards,

    Tanaka

  • +1 in reply to user4012620
    TI__Mastermind 24075 points

    Hi Tanaka,

       Sure, using a net-tie or 0 ohm resistor near the thermal pad is a valid way of connecting the AGND and PGND. Also the GND pin should connect to power ground.