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BQ79731-Q1: BQ79718 Question

Maor Matityahu
Intellectual 600 points
Part Number: BQ79731-Q1

Hello,

I am using the BQ79718 AFE and i have 2 questions:

1. I need to measure the battery pack current and i have 0-4V single ended analog signal that is related to the current. Can i connect it to GPIOx and measure the current with the AFE (by measuring the voltage)? What is the full scale ADC measurement of the AFE? 5 or 4V?

2. I have 12 NTCs in the battery pack but i have fewer GPIOs to read all of them. Can i use MUX and control the select pins of the MUX with the GPIOs of the AFE and connect the NTC reading (output of the MUX) to GPIOx?

Thank you

  • +1
    TI__Expert 7020 points

    Hi Maor,

    1. Yes, the GPIO pin can measure a 0V to 4V signal. 

    2. Yes, the 718 GPIO pins can be used to digitally control the MUX with 5V logic while another GPIO pin is used for measuring the MUX's selected trace.

    Regards,

    David

  • 0 in reply to David Ray
    Intellectual 600 points

    Hello,

    Thank you i have two more questions:

    1. In SHUTDOWN mode i saw that i can turn off AVDD by placing pull up to RX less than 20K. But how i wake up from SHUTDOWN if i dont have AVDD to supply the UART? In the datasheet it says that RX must not be above AVDD.

    2. What is the accuracy of the GPIO ADC pins in 25 deg and in temp?

    Thank you

  • 0 in reply to Maor Matityahu
    TI__Expert 7020 points

    Hi Maor,

    Maor Matityahu said:
    1. In SHUTDOWN mode i saw that i can turn off AVDD by placing pull up to RX less than 20K. But how i wake up from SHUTDOWN if i dont have AVDD to supply the UART? In the datasheet it says that RX must not be above AVDD.

    Turning off AVDD is used for stack devices. These devices can only be woken up by a wake ping through daisy chain communication. Turning off AVDD means the current draw in shutdown is less, but UART cannot be used to wake up the device. 

    Maor Matityahu said:
    2. What is the accuracy of the GPIO ADC pins in 25 deg and in temp?

    We provide the following for -40C to 125C in the electrical characteristics section of the BQ79718 datasheet:

    Regards,

    David