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BQ25798: CONV_OCP_STAT

Part Number: BQ25798
Other Parts Discussed in Thread: BQSTUDIO

Please let me check the definition of "converter" for CONV_OCP_STAT in REG20_FAULT_Status_0 Register.
Is it related to the ADC? Or is it about the function of the back-boost converter?
If you could show us the location of the converter on the evaluation board schematic, we would appreciate it.



Regards,
Kagawa

  • Hi Kagawa-san,

    The over current protection applies to power converter, so the converter refers to the integrated buck-boost converter of BQ25798.

    Regards,

    Eric

  • Hi Eric-san,

    Thank you for your reply.

    Is this threshold the following value?




    Question about the other register.

    The contents of bit-5 of BQ25798 datasheet 9.5.1.7 REG09_Termination_Control Register are different in Figure 9-32 and Table 9-20.
    Please tell us whether RESERVED or STOP_WD_CHG is set as the correct function of the IC.



    Regards,
    Kagawa

  • Hi Kagawa,

    IBUS_OCP refers to the over current protection of the input current to the buck-boost converter from VBUS pin.

    REG09[5] allows the host to configure the charger to automatically disable charge (set EN_CHG=0) when the watchdog timer expires or not disable and keep charging.

    Regards,
    Jeff

  • Hi Jeff-san,

    What are the conditions under which CONV_OCP_STAT is set?

    Regards,
    Kagawa

  • Hi Kagawa,

    If the power FETs hit cycle-by-cycle current limit (Q1,Q4 7.5A min and Q2,Q3 10A min) more than 7 times in a short period, CONV_OCP_STAT flag triggers.  Other over current protections (IBUS or IBAT) or SYS short almost always trip first.  I have only seen CONV_OCP occur during a power pin short event.

    Regards,

    Jeff

  • Hi Jeff-san,

    Othere questions.

    1) When transitioning between Ship Mode and IDLE state via i2c communication, is it OK to leave the /QON pin open?



    2) I would like to know about the operation of PFM mode.
    When I apply about 0.5A of current from the SYSTEM pin on the BQ25798 evaluation board, the efficiency is only about 83%.

    For your reference, we attach the results of our own checks.
    (1) The results with PFM enabled show that the efficiency is 83% under the following conditions when VAC2 = 12V input.
    (2) If the current flowing to the SYSTEM pin is increased to 0.8A, the efficiency will increase to 93%.
    (3) Even at 0.5A as in (1), if the "Disable PFM in Charge Mode" checkbox in bqstudio is checked, the efficiency will be about 93%.
    Currently, I have set PFM_FWD_DIS=0 with no battery connected, but if there is any setting to maintain high efficiency even at light loads, please let me know.

    ①No VBAT connection, VAC2=12V, Fsw=750kHz with L2=2.2uH, PFM Enabled, ISYS=505mA


    No VBAT connection, Fsw=750kHz with L2=2.2uH, PFM Enabled, ISYS=800mA


    No VBAT connection, Fsw=750kHz with L2=2.2uH, PFM Disabled, ISYS=500mA


    Regards,
    Kagawa

  • Hi Kagawa,

    Regarding 1, /QON should be left floating all the time and only pulled low to exit ship mode or force a power on reset.

    Regarding 2, unfortunately PFM is only helpful with very low currents closer to 100mA.  I am not surprised that PWM (PFM off) gives higher efficiency at 0.5A. Also, the transition point to enter PFM changes with VBUS to VBAT differential.

    BR,

    Jeff