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Why are BQ294512 inputs backwards?

Brian Boorman
Guru 25210 points
Other Parts Discussed in Thread: BQ34Z950, BQ29411, BQ294512

On the BQ29411 secondary overvolt protection IC and the BQ34Z950 gas gauge ICs, V1 is the cell at the top of the stack, and V4/V5 is the cell at the bottom of the stack.

Why did TI not follow this convention when designing the BQ294512 device (replacement for the BQ29411)? The new device has V1 as the bottom-most cell in the stack.

Nothing like cutting traces adding wires to a 50-piece prototype run of boards.

  • 0
    TI__Guru 54715 points

    The discussion of whether inputs/bits/bytes in electronics and computing should be numbered bottom up or top down is long with many strongly held opinions and arguments on both sides. Lately the view that there is always a cell 1 in a pack while there may not be a cell 3 or 4 or 6 or 10 has won out, so while many older parts are numbered top down, many newer parts are labeled bottom up with the idea that the lowest or first cell positive goes to VC1 and proceeds up the pack.

    There are other discussions on whether pins on a new part should be kept in the same location as historic devices or moved to try to provide a better layout or better performance.  When new features or options are added to a device in a family similar discussions also occur.  It is very frustrating to discover after boards are built that the pins are not where or what you expected as you indicate, or that the package is not the one you expected.  When changing to a new part number, even if the number difference is very subtle, please be sure to check the pin descriptions and package dimensions carefully.