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bq4850Y Questions

Paul Joseph
Expert 2795 points

Other Parts Discussed in Thread: BQ3285

For this IC, Section on Calibrating the Clock. I need to know more about the SOFTWARE CALIBRATION BITS.

1)     Are these CAL bits written in the same sequence as for the RTC time parameters? Does the Write Bit need to be set? And then, the Write Bit lowered to a zero for the Cal bits to be transferred?

2)     After changing the Calibration bits (Writing), is the RTC transition to the new setting seamless? Does the RTC values continue ticking without having to re-write the timing values?

3)     Are the Calibration bits shadowed as the other Timing Registers ( Sec, Minutes hours Day month year Etc)?

4)     If item 3 above is yes then to read the Calibration bits is it assumed the Read bits after setting, One must Raise the Read Bit and wait a second to read these bits?

5)     Is the part calibrated at the factory before shipping? If so how does on obtain the Cal bit setting, set the Read bit and wait a second and read?  Or just read the Cal bits with out setting the Read bit.

6)     If the cal bits are not set at the factory is it good practice to always start by writing these bits to zeros, Are they random when shipped?

Please advise, thank you.

  • 0
    TI__Mastermind 24205 points

    Hi Paul,

    I have reached out to the applications engineer supporting this device. Please expect a reply soon.

    Regards

    Arvind Sridhar

  • 0 in reply to Arvind Sridhar
    Expert 2795 points

    any update on this request

  • 0 in reply to Paul Joseph
    TI__Guru 71526 points
    Hi Paul,
    I have escalated this to the Apps team for this device.
    ~Leonard
  • 0
    TI__Guru 71526 points

    Paul,

      First, hoping the end-user realizes this is an obsolete device, NRND. 

    Next, if the clock either loses accuracy, or does not retain clock information, then the internal battery has been discharged. 

    I have attached the BQ4850Y Product Specification, which has the Clock settings, START/STOP commands, and CAL information.

    Just FMI, is this a new product design, or troubleshooting a problem with the existing product?

    ~Leonard 

       bq4850ySpecification .pdf

  • 0 in reply to LeonardEllis
    Expert 2795 points
    yes ,this is existing design, any comment on the 1-6 questions
  • 0 in reply to LeonardEllis
    Intellectual 435 points
    One Clarification, is for the calibration bits:
    1 Are they set at the factory? If not then are they random for each part or set to a know default?
    2 Are they also shadowed and hence updated when the READ bit is set to a '1'?
  • 0 in reply to Eric Mac
    TI__Guru 71526 points

    Hi Eric,

      This should answer the questions presented; again, wondering why the end-user is now asking these, as this product has been in production for many years?  Or, are they revising the design?  If so, we probably want to get involved to recommend an up-to-date device. 

    Q1) Are these CAL bits written in the same sequence as for the RTC time parameters? Does the Write Bit need to be set? And then, the Write Bit lowered to a zero for the Cal bits to be transferred?   A1> The CAL bits are not dual-port registers and therefore do not need the extra step which stops updates to the clock and alarm registers.

    Q2) After changing the Calibration bits (Writing), is the RTC transition to the new setting seamless? Does the RTC values continue ticking without having to re-write the timing values?  A2> Yes, the CAL bits will take immediate impact.  Note the section in the datasheet that discusses the test mode and enable bit FTE.  This test mode puts a 512Hz signal on the LSB of the date.  More in the Calibrating the Clock section.

    Q3) Are the Calibration bits shadowed as the other Timing Registers ( Sec, Minutes hours Day month year etc)?  A3> No shadow for the CAL bits. 

    Q4) If item 3 above is yes then to read the Calibration bits is it assumed the Read bits after setting, One must Raise the Read Bit and wait a second to read these bits?  A4> N.A. see A3. 

    Q5) Is the part calibrated at the factory before shipping? If so how does on obtain the CAL bit setting, set the Read bit and wait a second and read?  Or just read the CAL bits without setting the Read bit.  A5> Page one of the datasheet states:  “The battery is electrically isolated when shipped from the factory to provide maximum battery capacity.”  This means that no calibration is done at the factory – otherwise it would be erased when the battery is disconnected/isolated. 

    Q6) If the CAL bits are not set at the factory is it good practice to always start by writing these bits to zeros, Are they random when shipped?  A6> N.A. see A5. 

     ~Leonard

     

  • 0 in reply to Paul Joseph
    TI__Guru 71526 points

    you're welcome!  And perhaps the end customer may want to look at a redesign with the BQ3285 or the BQ4285 since the BQ4850Y is NRND.  Even though it may remain as NRND for months or years, and when it is converter to Obsolete you still have 1 year to place orders, it may be advantageous to update the design soon.

    ~Leonard