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BQ77915: Threshold programming

M Anand
Prodigy 240 points
Part Number: BQ77915
Other Parts Discussed in Thread: BQ25798, BQ77905

Hi,

I am planning a design for a 4S LiFePO4 system using the BQ77915, in conjunction with the BQ25798 charger, in accordance with a recent suggestion.

I have been reviewing the datasheet for the BQ77915 and I have what seems like a pretty basic question, but i can't seem to find the answer in the datasheet - apologies if I am missing something obvious.

Table 9-1 of the datasheet lists various functionalities, and mentions for example, that the OV threshold is " 3 V to 4.575 V (25-mV step)". How are these thresholds programmed? The 7 devices variant available, that are listed in Table 6-1, do not cover this whole range in 25 mV steps.

I see mention of an internal EEPROM that stores the thresholds in several places in the datasheet, but there seems to be no way to program it. So, if one wants some slightly different values than one of the variants available, is it something that one specially requests?

Thanks,

Best regards,

Anand.

  • 0
    TI__Guru* 81035 points

    Hi Anand,

    The threshold is only programmable in the TI factory, so a new threshold would require a new part number be created. There are a couple of new part numbers in development for LiFePO4 cells, but these will not be released until early 2023. Can you check the list of existing part numbers to see if one of these will fit your needs? There is also the BQ77905 which is similar but does not include the cell balancing feature.

    Best regards,

    Matt

  • +1 in reply to Matt Sunna
    Prodigy 240 points

    Hi Matt,

    OK, understood, that's what it seemed like, thanks for confirming.

    We do need the balancing - the 7791506 seems to come closest to the LiFePO4 ranges and seems like it would probably be OK for our application. Will check in the on the new part numbers next year as well.

    Thanks,

    Best regards,

    Anand.