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BQ24250 Standalone operation scheme

Marco Pappalardo
Prodigy 50 points
Other Parts Discussed in Thread: BQ24250, BQ24251, BQ27532-G1

Hi, I'm Marco,

I'm in the need of some informations about your device BQ24250. In the datasheet I've read it has two different working modes, standalone and I2C, but it is not explained how to connect the device to the system in both cases. The application showed is referred to BQ24251, which is moreover intended to be connected with USB connector.

In my application I use the device in tandem with BQ27532-G1 and I use pretty the same connection diagram (I only change the value of 2-3 resistors) but I have some questions:

- the connection scheme of the application is intended to be in a I2C working mode. If I want to make it works in a standalone mode what I need to change in the scheme? disconnect the EN1 and EN2 pins? Or I need to connect these pins to VCC and GND according to the truth table 1 in the datasheet?

- In the I2C case which voltage level corresponds to 1 bit and which one to 0 bit? I use a ATxmega128 with GPIO voltage level set to 1.8V, so I have a logical 1 near 1.8V and a logical 0 near 0V. It's good to communicate with BQ24250 or I need to adapt voltage levels? If it's yes, in which way?

  • 0
    TI__Guru**** 166426 points
    The bq27532-G1 acts as the I2C master for the bq24250. Whenever the bq27532-G1 is powered, it will place the bq24250 in host mode. Therefore, the ENx pins are irrelevant, unless set to ENx=1. I suggest using either ENx=0 or EN2=0 and EN1-1.

    1.8V is high enough for I2C logic high.
  • 0 in reply to Jeff F
    Prodigy 50 points

    Thanks Jeff for your fast answer.

    Just in the case i chose to set ENx=0, what should I do with pins ILIM and VDPM? Did I have to short to ground both pins to set the limits showed in Table 1?

    Thank you for your support.

  • 0 in reply to Marco Pappalardo
    TI__Guru**** 166426 points
    The ENx pins only control ILIM and VDPM while in standalone mode, i.e. when the gauge is not communicating with the charger. If you short ILIM and VDPM to ground you get ILIM=2A and VDPM=4.68V as the default in host mode, before any I2C writes to those registers.