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Original question:

BQ40Z60: BQ Chip causing high EMI and burns out if change gate driver resistors

BQ40Z50-R2: Discrete Charger Recommendation

Christopher Timperio
Prodigy 120 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z60, TPS3839, BQ24600, BQ40Z50, BQ29209, BQ25883, BQ25886, BQ25713, BQ24171, BQ25892, BQ24170, BQ24133

Hello,

Per this prevous forum thread: https://ticsc.service-now.com/csm?id=csm_ticket&table=sn_customerservice_case&sys_id=efb59adb1b1e8cd4d355ca217e4bcbaa&view=csp & https://e2e.ti.com/support/power-management/f/196/p/875348/3238382#3238382 ; since the BQ40Z50-R2 and discrete charger is recommended for a change from the BQ40Z60, I wanted to also ask if there is a discrete charger IC you recommend which is known to also have low emissions that works well with the BQ40Z50-R2.

Thank you,

Chris

  • 0
    Prodigy 120 points

    To follow up with some specifics about our application; I've seen chargers selected comparable to TPS3839 or BQ24600, however, there seems to be many options so I was hoping to get some feedback and select an actual charger IC based on our needs. 

    Our application is using 2 cells in series of the US21700VTC6A. Nominal voltage is 3.6V, but cells can be 4.2V when fully charged. Nominal capacity at 3.6V is 4100mAh. Please let me know if any other information is needed. 

    Thank you

  • 0 in reply to Christopher Timperio
    Prodigy 120 points

    One other thing, I'm not sure even the BQ40Z50 is even the correct IC we'd need for our application. For instance, I've also seen the BQ29209. Perhaps this would even be a more well suited monitoring IC for our application? However, does this IC also support charging, I guess is the main question?

    Thank you

  • 0 in reply to Christopher Timperio
    TI__Guru 52115 points

    Hi Chris,

    I suggest it would better for our charge team to answer your question. I will move your thread so that they can take a look.

    Andy

  • 0 in reply to Andy Liu (BMS)
    TI__Guru**** 166916 points

    Hi Andy,

    I am not aware of a monitor/protector/gauge/charger integrated IC.  With a little more information (charger input voltage and current, desired charge current, host controlled or standalone), I can recommend a charger.  To confirm, you have 2 series cells for 8.4V termination voltage?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 120 points

    Hi Jeff,

    Thanks for the reply. Yes, we have at max 8.4V when cells are fully charged. When nominal, it's more like 7.2 / 7.4V. To be more specific, we're really looking for a replacement for the BQ40z60. We were told to go with the BQ40z50 and a discrete charger, so I would like to identify that substitute charger which would replace the charger inside of the BQ40z60.  So it should have similar specs to the internal one there.

    Thanks,

    Chris

  • 0 in reply to Christopher Timperio
    TI__Guru**** 166916 points

    Chris,

    I can help but I need more info:

    Input voltage range

    Max desired charge current

    Host (I2C) controlled or standalone, resistor settable charger

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 120 points

    Hi Jeff, 

    Thanks for the reply. 

    Input voltage range: 3.2V to 4.2V per cell. Since pack is 2 cells in series, it's 6.4V to 8.4V range.

    Max desired charge current: 1C: 4A

    Charger: Perhaps standalone, however, we do not have a strict requirement here. Ideally, the simplier and less complex option, which I'm assuming is standalone, something requiring less complex supporting circuitry. And main requirement is something with good or low EMI.

    Thanks,

    Chris

  • 0 in reply to Christopher Timperio
    TI__Guru**** 166916 points

    Hi Chris,

    For input voltage, I need the power source voltage for the charger, for example, 5V USB, 12V wall wart, etc.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 120 points

    HI Jeff,

    Oh, I was assuming the charger would be IC based, so like a small chip. Is this not the case?

    If it is an IC, we have 5V as our input. Or can also produce higher as needed. 

    Thanks,

    Chris

  • 0 in reply to Christopher Timperio
    TI__Guru**** 166916 points

    Chris,

    Going from 5V to 8.4V, TI only has a limited number of boosting charger ICs:

    BQ25883 host controlled - 2A charger current - need 2 in parallel (there is also a standalone version BQ25886).

    BQ25713 host controlled controller with external FETs

    If you can boost your input voltage to at least 9V, we have several buck based chargers that could work including the two below:

    BQ24171 standalone 4A charger

    BQ25892 host controlled 5A charger

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 120 points

    Thanks Jeff.

    So if we went with the BQ25883 since it looks the least complex, what are disadvantages of having two charger IC's in parallel to meet the 4A charging requirement? Could this be dangerous for either the IC or battery? Would we need some sort of diode protection to prevent current from flowing back into either charger, or is that not a concern?

    Also, it would connect in parallel as well to the BQ40z50, I'm assuming?

    Thanks

  • 0 in reply to Christopher Timperio
    TI__Guru**** 166916 points

    Hi Christopher,

    You can connect the BQ25883 BAT pins together but not the SYS pins.  Do you even need the SYS output to drive other system circuitry?  If so, then you can only use SYS from one of the chargers.  Any system load could reduce charge current and the SYS voltage will be the higher of MINSYS or slightly higher than the regulation voltage.  Also, I just redid the math and 2 BQ25883's in parallel will struggle to provide 4A up to 8.4V.  Their max input current is 3.2A and you will need more than 8.4V*4A/5V = 6.72A/=3.36A to get 2A charge current out of each.  You would need to up your charger input voltage to at least 5.5V.   

    On the input side, you need to make sure the VINDPM feature of one charger is set higher than the other.  Full disclosure, we have never paralleled this boost converter but have done it successfully with several of our buck based converters.  I see no reason why it would not work the same.

    If you are going to have to change your input supply anyway, I think creating a 9V+ supply and using 2 BQ24133's in parallel might be a better choice.  If you don't have a heavy system load for the 9V+ supply, you can simplify down to the figure below and even replace FET Q1 with a diode.  Another benefit is the BQ24133 P2P with the BQ24170, 4A charger.  So, with good heat sinking ground area connected to the charger's IC exposed pad, you might find that the 170 doesn't get too hot and you only need one charger.

    Regards

    Jeff