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BQ76952: The consideration for OPT[2]

Beginner
Intellectual 2421 points
Part Number: BQ76952

Hi Team,

In TRM, we can find the following description in OPT[2]. I am interested in the note - This should only be selected if OPT[3] = 0 and OPT[1] = 0.

Could you explain the reason? Thanks for your help in advance. 

  • 0
    TI__Guru 54715 points

    Hi Beginner,

    The BQ76952 has several multi-function pins named with their primary use but with various configuration bits which change based on the selected function.  As an example see table 6-5 of the technical reference manual compared to table 6-6.  The hierarchy of the bits is not explained other than the notes.  For OPT[2] as shown above:

    If OPT[1] = 1 the pin would be driven to a high state, so the pull up of OPT[2] would not be effective, apparent, or desired.

    If OPT[3] = 1 the pin would be driven to REG1 if driven.  It is not clear why this bit would have an effect if OPT[1] were 0, but it is easy enough to set.

    So for the 3 bits OPT[3,2,1] the practical settings would seem to be:

    0,0,0: No pull up, high impedance when "high", use with external pull up.

    0,1,0: Weak internal pull up to REG1 when "high"

    0,0,1: Driven to REG18 when "high"

    1,0,1: Driven to REG1 when "high"

    others: not recommended