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BQ76930: 7 cell Battery monitor and protection Using BQ76930 and bq78350

christos christou
Intellectual 270 points
Part Number: BQ76930
Other Parts Discussed in Thread: BQ78350, CSD, , TIDA-00449, BQ78350-R1, BQ76940

Hello "World", for my battery bank i have posted to before because i was looking for battery protection and cell balance i find out the BQ76930 is very intersting complete features for cell balance OV UV OT and UT, OCD CSD protections, but i couldn't find a good reference design, because in the datasheet BQ76930 schematic is pretty simple and is used with BQ78350 companion controller, there is no N-FET in every VCx pin and a diode, why is BQ78350 used as companion controller?.
but in TIDA-00449 the Schematic is very complex every VCx pin as A N-fet and a diode and plus it's used with MSP430.
in my project it's a battery pack for a USB-c using cypress MCU for USB-c controller, is it possible to use BQ76930 with cypress CYPD3171 as companion controller Using I2c (SDA and CLK) only to send the battery level to the MCU(CYPD3171) ?

  • 0
    TI__Guru* 81035 points

    Hi Christos,

    There are two options that are popular for different reasons. The BQ78350-R1 is designed specifically to work with the BQ76930 monitor family, so there is no need to write your own code. The BQ78350-R1 is also a battery gauge, so if you need to track the state of charge and remaining capacity of the battery, it is very useful.

    However, the BQ78350-R1 is not very flexible. It does have some flexibility because there are hundreds of configurable parameters in data flash, but you cannot change the algorithms. Some applications need more flexibility because of unique requirements. That is where the 2nd option of a microcontroller is often a good fit. It is much more development work on the software side, but you have complete control.

    There are currently 5 reference designs available for this monitor family. They are spread across the BQ76930 and BQ76940 product folders, but there is a short summary of these designs near the beginning of this video: https://training.ti.com/how-create-schematic-bq76920-bq76930-and-bq76940 (or Youtube: https://www.youtube.com/watch?v=B5dsIc2C_xA).

    I am not familiar with your MCU, but it should work if it has an I2C interface. Make sure to select the correct version of the BQ76930 - see the part number listing near the beginning of the datasheet. You can select the device based on the REGOUT voltage, I2C CRC, and I2C address.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 270 points

    Hello Matt, thank so much for the answer it made take the decision directly, i would like to use BQ78350-R1  with the BQ76930 so can track battery state of charge and remaining capacity, of the battery. is necessary to have FET in every VCx pins  and diodes between them or just CC capacitors will be enought and Rc resistors ?

  • 0 in reply to christos christou
    TI__Guru* 81035 points

    Hi Christos,

    The FETs are optional, but these are needed if you need more balancing current than the device can provide directly. So it really depends on your cell balancing requirements. Section 4 of this app note can help you decide which way to go: http://www.ti.com/lit/an/slua749a/slua749a.pdf

    Best regards,

    Matt