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BQ24296: Stand alone mode

Kagen Aeby
Prodigy 60 points
Part Number: BQ24296
Other Parts Discussed in Thread: BQ24075, BQ25895, BQ24295, BQ25616

When comparing different chips, the BQ24296 is marked as I2C or stand alone function. I want to incorporate this as a stand alone device for battery charging in a power bank device. I had a few questions regarding this. 

Should I leave the host pins such as SDA, SCL, and INT floating?

I don't intend to use the thermal battery monitoring, what do I do with the TS pin? Connect the pin to a voltage divider as per the datasheet but use a 10k resistor instead of the thermistor?

  • 0
    TI__Mastermind 21725 points

    Hello, 

    Thank you for reaching out via E2E. Firstly I want to bring to your attention that since you plan to use the BQ24296 as a standalone device the default charging settings are used and cannot be modified. These settings are listed in table 9-4 on page 24 of the datasheet. Please find my comments regarding your questions below. 

    Kagen Aeby said:
    Should I leave the host pins such as SDA, SCL, and INT floating?

    Yes please leave SCL, SDA, and INT floating if pins are not to be used. 

    Kagen Aeby said:
    I don't intend to use the thermal battery monitoring, what do I do with the TS pin?

    If TS pin function is not to be used please connect TS pin to a voltage divider where RT1 = 10kohm and RT2 = 10kohm. The 3rd resistor marked RTH in datasheet figure 9-7 is therefore not needed. 

    Best Regards,

    Garrett 

  • 0
    Prodigy 60 points

    Hi Garrett,

    Thanks for your answer, I appreciate you! 

  • 0 in reply to Garrett Kreger
    Prodigy 60 points

    I did have another question regarding VBUS vs PMID. 

    As previously mentioned, the device I'm designing is intended to be a powerbank with two USB type C ports. Taking a look at this article https://e2e.ti.com/blogs_/archives/b/fullycharged/posts/power-bank-basics, It looks like 5V flows out of PMID, so based on that, it looks like I should route my downstream type C port power controller to PMID. However, looking at the typical application in the datasheet for the BQ24296, the PMID is just connected to a capacitor to ground. 

    The other question I had is in regards to shipping mode. My previous design was utilizing the BQ24075 as the battery charger, but I am running into problems where it is unable to charge bc1.2 devices, and would keep cutting off power to the plugged in device after a second. This design had a SPDT switch to cut battery utilizing the SYSOFF pin. With the BQ24296 being utilized as as a stand alone device, could I use the QON pin for the same function? 

  • 0 in reply to Kagen Aeby
    TI__Mastermind 21725 points

    Hi Kagen, 

    Please see my comments below regarding your 2 questions.

    1) Since you are designing a power bank application you may want to use the BQ24295 or BQ25895 instead of the BQ24296. The key difference between these parts is that on the BQ24296 the boost mode output is to VBUS and PMID (Q1 reverse blocking FET is on) verse on the BQ24295 and BQ25895 the boost mode output is only to PMID (Q1 reverse blocking FET is off). 

    If you want your device to operate the same as what is shown in figure 4 of the article you linked you will want to use the BQ24295 or BQ25895 so the PMID output is separated from the VBUS input. 

    2) Unfortunately ship mode cannot be entered if you are using the device in standalone operation. On all 3 devices I have mentioned an I2C write is needed to enter ship mode and then QON pin can be used to exit shipmode.  

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 60 points

    How can you tell from the Datasheet? The functional block diagrams for the 24295 vs the BQ24296 look basically identical. How about the BQ25616? Is the boost mode output to VBUS and PMID, or only to PMID?

  • 0 in reply to Kagen Aeby
    TI__Mastermind 21725 points

    Hi Kagen, 

    In each datasheet please refer to the "Boost Mode Operation from Battery" section. On the BQ24295 datasheet this section is on page 17. The section will specify if boost mode operation output is specifically PMID or if boost mode output is "through USB port" meaning both VBUS and PMID pins.

    The typical application section near the end of each datasheet will also help to indicate if PMID is the boost output. For example, on both the BQ24295 and BQ25895 datasheets the typical applications figure shows a dashed block "phone" to indicate the OTG boost output is PMID. 

    BQ25616 has boost mode output to both VBUS and PMID. 

    Best Regards,

    Garrett