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BQ25798EVM: BMS034A

POORTI VARSHNEY
Prodigy 60 points
Part Number: BQ25798EVM
Other Parts Discussed in Thread: BQ25798

Hello Jeff,
We have observed following observation while performing the tests on BMS034A(EVAL BOARD BQ25798):
-> When the Power is given from the Power Input Terminal & the Pull up connector (JP30) is connected then the Stat LED blinks and the voltage at the battery terminals fluctautes.(Note: For prog resistor 27Kohm , JP29 is connected, Output voltage fluctuates between ~12 & ~14).
-> When we disconnect the pull up connector (JP30) then the stat led stops blinking and we get the stable voltage at the VBAT (16.9V).
We oberved that the problem is creating when the 3V3 & VBUS both are on.

Thanks & Regards

Poorti Varshney

  • 0
    TI__Guru**** 165886 points

    Hi Poorti,

    With no battery connected and charge enabled, the pulsing SYS and BAT output are expected.  If charge is disabled, either by /CE pin pull up or CE bit =0 or TS pin fault when pack with thermistor is removed, the output is stable.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 60 points

    Hi, Jeff

    When we connected the Battery , then the stat LED is constanty on.

    What could be the probablr eeason for the same. According to data sheet the High state of STAT LED signifies that the chrging is disabled or the charging is completed but in our case none of the above mentioned case is there.

    Regards

    Poorti

  • 0 in reply to POORTI VARSHNEY
    TI__Guru**** 165886 points

    Hi Poorti,

    With valid power voltage at VBUS and battery with voltage < VREG, final battery regulation voltage, the charger is charging, open drain STAT line is low because the charger is charging the battery.

    If STAT is high, you are correct that either charge has terminated (ie, the voltage sensed the charger's BATP pin = final battery regulation voltage) or /CE pin = high or CE register bit = 0.

    Can you provide a register dump of the charger? The status and/or fault bits report what is/has happened.  Note that the fault bits clear after being read. If you can enable the charger's ADC before the register read and dump, that will give me your setup voltage and currents.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 60 points

    Hi jeff,

    I want to know what exact registers you want?

    Also , in our customised board having BQ25798 , followed same design as provided for the evaluation board. We are facing following problems:

    1) When we give the power from the Input(5V keeping current limit  1A), the IC starts giving voltage but with fluctauting voltage between 12 & 13. The Vsys also fluctuates . After some time it got stuck and current consumption from the source side set upto 100mA and then the output voltage sets up to 16.9 as desired. But when we starts giving vottage at 3V3 then it the fluctuation again starts and the stat LED starts blinking.(PROG RESISTOR 27kohm)

    2) We read the FAULT_FLAGREG0 0x26  and we found  below results:

    DATA 0X20
    IBAT_REG_FLAG 0 Normal
    VBUS_OVP_FLAG 0 Normal
    VBAT_OVP_FLAG 1 Enter VBAT OVP
    IBUS_OCP_FLAG 0 Normal
    IBAT_OCP_FLAG 0 Normal
    CONV_OCP_FLAG 0 Normal
    VAC2_OVP_FLAG 0 Normal
    VAC1_OVP_FLAG 0 Normal

    2) We are unable to configure what could be the issue.

    please help me out.

    regards

    Poorti

  • 0 in reply to POORTI VARSHNEY
    TI__Guru**** 165886 points

    Hi Poorti,

    If the input power source is 1A current limited, then the charger's input current limit register must be set to 1A or less.  The EVM defaults to input current limit register clamped to 1.5A or less due to ILIM_HIZ pin resistor divider.

    Is a battery or battery simulator attached to BAT pin? With no battery or battery simulator connected and charge enabled due to /CE pin=GND and CE register bit=1 and no TS pin fault, the SYS and BAT outputs fluctuate as the BAT pin capacitance charges up to termination, discharges, recharges, and repeats.

    Regards,
    Jeff