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BQ34Z100-R2: Question about circuit configuration

?? ??
Prodigy 30 points
Part Number: BQ34Z100-R2

Tool/software:

Hello,

I have a few questions:
①Is the VEN pin an open-drain output?
　The datasheet states "Open-drain I/O pins (SDA, SCL, HDQ, VEN)".

②The recommended value for the current sense resistor is 5mΩ to 20mΩ, but can I exceed this value?
　For a load current of about 0.1A, can I reset the resistance value beyond the recommended value so that the current sense input potential difference is within ±125mV?
　For example, a resistance value of 0.5Ω.
　I understand that even if a peak current occurs, the potential difference must be kept below ±300mV.

③If the temperature reference is the internal thermistor of the BQ34Z100-R2 instead of an external thermistor, is it okay to float the TS pin since it has a built-in pull-down resistor?

④If two PchFETs are connected in a common source configuration on the BAT+ side for reverse connection protection, will this IC be damaged if the battery polarity is incorrect?
　On the BAT+ side, two PchFETs are connected in a common source configuration for reverse connection protection, the battery voltage is stepped down, and DC3.3V is supplied to the REGIN pin.
　The voltage to the BAT pin is also connected to a voltage divider resistor circuit, with the battery voltage passing through a reverse connection protection circuit.
　Is this a problem?

⑥Is it correct to understand the connections of SRN and SRP to PACK- and BAT- as shown in the image below?
　RL is the load.
　

Thanks.

  • 0
    TI__Mastermind 26945 points

    Hello,

    This question has been assigned and will be reviewed when possible.

    Thank you,
    Alan 

  • 0 in reply to Alan Frias
    TI__Mastermind 26945 points

    Hello,

    ?? ?? said:
    ①Is the VEN pin an open-drain output?
    　The datasheet states "Open-drain I/O pins (SDA, SCL, HDQ, VEN)".

    -The  VEN pin is configured as as output and input all of the time. It will pulse to 2.5V every 1 second when the voltage measurements are taken. It also sinks current when pulled to 2.5V externally. 

    ?? ?? said:
    ②The recommended value for the current sense resistor is 5mΩ to 20mΩ, but can I exceed this value?

    -Yes it is possible to exceed that value, if you do so you will have a higher accuracy for your current readings

    ?? ?? said:
    f the temperature reference is the internal thermistor of the BQ34Z100-R2 instead of an external thermistor, is it okay to float the TS pin since it has a built-in pull-down resistor?

    -Although there is a internal thermistor and a external thermistor can be seen as optional we still heavily recommend to use a external thermistor that is close to the cells since temperature is a important value that we take into the algorithm.

    ?? ?? said:
    If two PchFETs are connected in a common source configuration on the BAT+ side for reverse connection protection, will this IC be damaged if the battery polarity is incorrect?

    -Can you better explain what you mean by "PchFETs", there is no reverse connection protection and you will damage the gauge

    ?? ?? said:
    ⑥Is it correct to understand the connections of SRN and SRP to PACK- and BAT- as shown in the image below?

    -You are missing the supporting components for the SRN and SRP but either than that it has no obvious errors.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    Prodigy 30 points

    Hi Alan,

    Thank you for reply.

    ①

    Alan Frias said:
    -The  VEN pin is configured as as output and input all of the time. It will pulse to 2.5V every 1 second when the voltage measurements are taken. It also sinks current when pulled to 2.5V externally. 

    In other words, does it mean that a pull-up resistor is not necessary for VEN?
    Or does it have an internal pull-up resistor?
    If it does have an internal pull-up resistor, please tell me what that resistance value is.

    ③Because the battery is charged and discharged at a low current, the temperature rise of the external thermistor is minimal and therefore has little impact, and because the temperature change due to the environment is predominant, I are trying to rely on the internal thermistor.

    ④Battery power is supplied to the BAT and REGIN pins via a load switch with reverse polarity protection such as the TPS2660. Although there is a voltage drop due to the Ron of the FET, it is small and I think the impact is small.
    In this case, would the following my question be a problem?

    ?? ?? said:
    If two PchFETs are connected in a common source configuration on the BAT+ side for reverse connection protection, will this IC be damaged if the battery polarity is incorrect?
    　On the BAT+ side, two PchFETs are connected in a common source configuration for reverse connection protection, the battery voltage is stepped down, and DC3.3V is supplied to the REGIN pin.
    　The voltage to the BAT pin is also connected to a voltage divider resistor circuit, with the battery voltage passing through a reverse connection protection circuit.
    　Is this a problem?


    Thank you.

  • +1 in reply to ?? ??
    TI__Mastermind 26945 points

    Hello,

    ?? ?? said:
    In other words, does it mean that a pull-up resistor is not necessary for VEN?
    Or does it have an internal pull-up resistor?
    If it does have an internal pull-up resistor, please tell me what that resistance value is.

    -As per the example schematics you don't need a pull up resistor for the VEN pin

    ?? ?? said:
    ③Because the battery is charged and discharged at a low current, the temperature rise of the external thermistor is minimal and therefore has little impact, and because the temperature change due to the environment is predominant, I are trying to rely on the internal thermistor.

    -That is a user decision and a the internal thermistor can work as the main temp sensor but you will lose out to resolution as well

    ?? ?? said:

    ④Battery power is supplied to the BAT and REGIN pins via a load switch with reverse polarity protection such as the TPS2660. Although there is a voltage drop due to the Ron of the FET, it is small and I think the impact is small.
    In this case, would the following my question be a problem?

    There is no obvious reason why this shouldn't work within your system

    Thank you,
    Alan