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BQ79731-Q1: BQ79718V Question

Maor Matityahu
Intellectual 490 points
Part Number: BQ79731-Q1

Tool/software:

Hello,

I am using the BQ79718V AFE and i use 15 cells of 3.2V each which is 48V.

I have some questions:

1. In active mode the LDOIN pin i consumes 10mA, why is that? i saw that in the datasheet it says 6mA

2. Is it ok to use external power supply (like buck) of 6V to the LDOIN pin to reduce the power consumption of the external fet? because if i use the external fet the power consumption is 48V*10mA, and if i will use another power supply the power consumption will be 6V*10mA

3. i want to turn off the 6V power supply to the LDOIN in shutdown mode. Is it ok to do that? Is it ok to turn off the LDOIN voltage and still apply voltages to BAT, CB15,VC15, etc..?

4. In the case of using external 6V supply, what to do with the NPNB pin?

Thank you

Maor Matityahu

  • 0
    TI__Prodigy 470 points

    Hey Maor,

    1. How are you measuring LDOIN? Is I_ACT(IDLE) normal between 5-10mA? And which specification in the Datasheet are you referring to with 6mA?

    2. Yes, you can use an external DC-DC or Buck, as long as it provide a stable ~6.1V to LDOIN.

    3. Leave NPNB floating. The reason behind the request of LDOIN to be a little higher than 6V is to prevent NPNB from increasing the basing voltage to regulate NPN BJT which is not being used. 

    Best regards,

    Abdel

  • 0
    Intellectual 490 points

    Hi Abdel,

    Thank you for your answers.

    1. What is the range of the LDOIN voltage i can put?

     2. i can also apply 8V to NPN and then to LDOIN? What is the better way this or 6.1V?

    3. I need to turn off the 6V power supply when the circuit is in sleep mode. Then i will not get supply to the LDOIN. In this case the AFE will go to shutdown or do i need to send a command to enter shutdown before turning off the 6V power supply?

    4. If i enters shutdown mode and the AVDD is still on (because of the 100k ohm pull up), and then i turns off the 6V power supply, then the AVDD turns off? After returning the 6V power supply the AVDD will come back?

    Thank you

    Maor Matityahu 

  • 0 in reply to Abdelrahman Aldmour
    Intellectual 490 points

    Hi Abdel,

    Thank you for your answers.

    1. What is the range of the LDOIN voltage i can put?

     2. i can also apply 8V to NPN and then to LDOIN? What is the better way this or 6.1V?

    3. I need to turn off the 6V power supply when the circuit is in sleep mode. Then i will not get supply to the LDOIN. In this case the AFE will go to shutdown or do i need to send a command to enter shutdown before turning off the 6V power supply?

    4. If i enters shutdown mode and the AVDD is still on (because of the 100k ohm pull up), and then i turns off the 6V power supply, then the AVDD turns off? After returning the 6V power supply the AVDD will come back?

    Thank you

    Maor Matityahu