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Original question:

BQ40Z50-R2: BQ40Z50-R2 Decoupling Capacitors

BQ40Z50-R2: CHG, DSG FET Drive

Liu Yang
Expert 8745 points
Part Number: BQ40Z50-R2

Hi Team,

Please help me answer the follow question from my customer, thank you so much.

I would like to know the electrical characteristics of "CHG, DSG FET Drive", especially V(FETON), in case of VCC = 7.4V.
In the datasheet, we can see that of VCC = 14.4V in section 7.18.

Best Regards,
Tom Liu

  • 0
    TI__Mastermind 42535 points

    Hi Liu,

    We don't have the values for VCC of 7.4V. However, the chg and dsg pin are driven by a chg pump that will maintain the drive at 10V greater than the PACK voltage to provide FET turn on.At >3.1V, power input switches from VCC to BAT for the gauge. So your drive is not via VCC. Please see table 7.6 and pin diagram in page 5 for power supply control.

  • 0 in reply to Batt
    TI__Expert 8745 points

    Hi Batt,

    Thank you for your answer.
    I'm sorry that I mistook VCC for VBAT. The background of this question is below:
    It uses 7.4V because two lithium ion batteries are used in series.
    (Strictly speaking, since there is a diode step-down, I think that the input voltage to BAT will be around 6.4V.) Please tell me the spec of V(FETON) (@7.18 CHG, DSG FET Drive) when VBAT=7.4V?

    Best Regards,
    Tom Liu

  • 0 in reply to Liu Yang
    TI__Mastermind 42535 points

    Hi Tom,

    The chg pump will try to keep the CHG and DSG pin at +10V in relation to the PACK+ pin to keep the FETs fully on and minimize Rdson.