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bq25898: bq25898: REG0F for Vsys

Hui Shao
Prodigy 30 points
Part Number: BQ25898
Other Parts Discussed in Thread: BQSTUDIO

Hi-

I am evaluating the bq25898 demo board. While I can read REG14, REG11 etc register correctly, the reading of REG0F is always 0 no matter the charger is connected or not.

The battery is pretty much fully charged and 3.98v is measured over Vsys headers.

What could be the reason that causes the Vsys reading is 0?

thanks!

Hui

  • 0
    TI__Guru 57721 points

    What is the VBUS voltage? Were you doing one-shot conversion? You should set the CONV_START bit (REG02[7]) to "1", then read the ADC registers. Thanks!

  • 0 in reply to Ning T
    Prodigy 30 points

    Hi Ning

    Thanks for reply. I set the CONV_RATE and got the reading of Vsys. BTW, what is the difference of one-shot conversion and continuous conversion? The latter will consume more power?

    Another question is, if I check status of bq25898 with bqstudio, it shows "NOT CHARGING" with adaptor is connected. What could be the reason blocks  it from charging?

    The fault register REG0C shows WDT expired and TS hot. The STAT led is blinking on demo board.  Are they the cause?

    Thanks!

    Hui

  • 0 in reply to Hui Shao
    TI__Guru 57721 points

    For one-shot conversion (CONV_RATE = 0), the battery monitor only provides conversion result for one time after the CONV_START bit is set to "1".

    For continuous conversion (CONV_RATE = 1), the battery monitor provides conversion result every 1 second automatically.

    When TS has fault, charge is disabled.

    When Charge suspend (Input overvoltage, TS fault, timer fault, input or system overvoltage) or Boost Mode suspend (due to TS Fault), STAT pin blinks at 1 Hz.

    Thanks!

  • 0 in reply to Ning T
    Prodigy 30 points

    Hi Ning,

    Thanks for the explanation! The board is back to charge normally.

    Another question is about INT of charger: when I plug in adapter, I got two INT pulses and when I remove the adapter, I got only once. Why?

    In addition, I see INT is triggered from time to time. There is really nothing got changed: adapter is connected, battery charger terminated. Why  some events are generated to notify host?

    thanks!

    Hui

  • 0 in reply to Hui Shao
    TI__Guru 57721 points

    The following events will generate 256-μs INT pulse:

    1) Good input source detected

    – VBUS above battery (not in sleep)

    – VBUS below VACOV threshold

    – VBUS above VVBUSMIN (typical 3.8 V) when IBADSRC (typical 30 mA) current is applied (not a poor source)

    2) USB/adapter source identified (through PSEL or DPDM detection, with OTG pin)

    3) Input removed

    4) Charge Complete

    5) Any FAULT event in REG0C

    When an adaptor plugs in, the two INT pulses are due to 1) & 2); When the an adaptor is removed, the one INT pulse is due to 3).

    The INT pulses can also be generated by 5) including watchdog timer expiration.

    Please check "Verified Answer" if this helps. Thank you very much!