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BQ24064: About BAT pin

Tsukui Yusuke
Guru 21930 points
Part Number: BQ24064
Other Parts Discussed in Thread: BQ24061, BQ24088, BQ24085, BQ24010, BQ24014, BQ24012, BQ25611D

Hi,

Customer has to insert a diode between the OUT pin and the battery for application reasons.
I will attach an image diagram.
Is it possible to use it in this way?
And Please let me know if you have any concerns.

Candidate devices are:
BQ24064 , BQ24061 , BQ24088 , BQ24085 , BQ24010 , BQ24014 , BQ24012
All of these devices have a BAT pin.

Also, please tell us other recommended devices.



Regards,
Yusuke

  • 0
    TI__Mastermind 22750 points

    Hi Yusuke,

    As noted in the schematic, the Vf drop may not allow for the battery to properly charge to the regulation voltage. Is the resistor intended to be used as a sense resistor? Can you provide more information on the use of the diode?

  • 0 in reply to Anthony P Pham
    Guru 21930 points

    Hi Pham,

    Thank you for your response and support.

    >Is the resistor intended to be used as a sense resistor?

    This refers to the resistors recommended by the respective data sheets.

    >Can you provide more information on the use of the diode?

    It has been decided that a diode must be installed. However, the type has not been decided.
    How much Vf is allowed?

    >As noted in the schematic, the Vf drop may not allow for the battery to properly charge to the regulation voltage.

    We believe that Vf drops can be canceled by using the BAT or BATSNS pins.
    For example, I think the BQ25611D can cancel the IR drop by connecting the BATSNS pin directly to the battery.
    Is this kind of usage possible with the BQ24xxx series?



    Regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 22750 points

    Hi Yusuke,

    This looks like it should work in theory. If you can tell more about the diode application besides it being required (is it used as device protection?) I may be able to see if there is a better device. 

  • 0 in reply to Anthony P Pham
    Guru 21930 points

    Hi Pham,

    Thank you for your kind support.
    Diode part numbers are as follows.
    They want to connect three diodes in series.
    The background of the installation is to comply with explosion-proof standards.

    ・RBS2LAM40C

    Regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 22750 points

    Hi Yusuke,

    This may not work if the diode creates a voltage drop that is below the battery regulation voltage. The battery will charge to the voltage after all the diodes (VBAT - 3x Diode Drop). If it is not the regulation voltage, this may cause the safety timers to trip after some time. 

  • 0 in reply to Anthony P Pham
    Guru 21930 points

    Hi Pham,

    Thank you for your response.
    I reported your advice to the customer.
    I got an additional question from a customer.

    1．
    >The battery will charge to the voltage after all the diodes (VBAT - 3x Diode Drop). 
    BATSNS will cancel the diode drop.
    As a result, the BAT voltage with the diode drop added is output to maintain 4.2V.
    Could you tell me the upper limit of OUT pin output?
    For example, can the OUT pin output 5.2V if a high input voltage is secured?

    ２．
    > If it is not the regulation voltage, this may cause the safety timers to trip after some time. 
    Thank you for telling me about the safety timer.
    What kind of state does ” If it is not the regulation voltage” assume?
    And Could you elaborate on the working conditions of the safety timer you envision?

    Regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 22750 points

    Hi Yusuke,

    After consulting with other members of the team, it looks like this should work, please ignore my previous concerns regarding safety timer. 

    I can only provide what is shown on the datasheet.