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Original question:

BQ25798: BMS034A

BQ25798: BQ25798

POORTI VARSHNEY
Prodigy 60 points
Part Number: BQ25798

Tool/software:

Hello Jeff,

Actually after continuous experimentation of the Circuit that we created with BQ25798.  I observed that the output Voltage is coming 10.11V even though the prog registor is placed 17.4kohm and at VSYS I am getting 12.1V. the circuit is been designed for 4s battery charging purpose.

At PMID side, getting the same voltage as the VBUS & at REGN , I am getting the same as VBUS. Across the inductor I am getting 3.12V if the VBUS is  at 5V.But as per the ideal case should be 16.8V & I am getting 10.11 V 

Could you please help me out in letting me know the cause for the same. Would be great of you.

Thanks & Regards

Poorti

  • 0
    TI__Guru**** 154896 points

    Hi Poorti,

    The 4S settings with PROG resistor = 17.4kohm are shown below:

    Not sure what you mean by "output voltage" but the SYS should be around 12V if battery voltage is below that value or not attached.  If VBUS=5V then REGN will also be 5v or slightly below.  If there is no battery attached and charge is enabled (not in TS fault due to missing thermistor), then BAT and SYS are likely pulsing up slightly above 16.8V, with SYS not dropping below 12V. If charge is enabled and battery is attached, charge termination occurs when V(BAT)=16.8V. 

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 60 points

    Hello Jeff,

    By output voltage I mean the VBAT voltage.

    Thanks & Regards

    Poorti

  • 0 in reply to POORTI VARSHNEY
    TI__Guru**** 154896 points

    Hi Poorti,

    Max battery voltage is VREG.  V(SYS) varies from MINSYS voltage to slightly above VREG.

    Regards,

    Jeff