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BQ76952: the question of CHG

?? ?
Prodigy 10 points
Part Number: BQ76952

Tool/software:

Hi,
I measured a StackVoltage-like value (45V 12s)  in CHG pin in normal mode(CHG already off).
I got a voltage higher than stack voltage about 11V when I enable CHG FET(It is working normally).
So I wanna know `a StackVoltage-like value (45V 12s)  in CHG pin when CHG off` is a normal case?
  • 0
    TI__Genius 17835 points

    Hello User,

    Where are you measuring that you are getting a voltage higher than stack voltage of around 11V? Have you also calibrated your stack voltage? If not, BQ769x2 Calibration and OTP Programming Guide can be useful. Is this measurement also with a DMM?

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 10 points

    Hi Alexis：

    The CHG output high level of BQ76952 is Vbat+11V, and the low level is Vbat. 

    Can I configure software so that when CHG is turned off, the CHG level is 0V?

    Or can I use a resistor to pull CHG down to 0V? Is this recommended?

  • 0 in reply to ?? ?
    TI__Expert 3425 points

    Hello,

    We have received your request and will work to answer it as soon as possible. 

    Our normal support team is OOO and will be returning 12/10 to help with any ongoing inquiry. 

    We appreciate your patience and understanding.

    Best, 

    -Luis Torres (PME

  • 0 in reply to ?? ?
    TI__Genius 17835 points

    Hello User,

    Thank you for your patience.

    It is normal for the CHG pin to be ~11V higher when it is ON.

    The CHG pin connects to the BAT pin internally when the CHG FET is OFF and connects to CP1 when it is ON. The overdrive level of the charge pump can be set to 5.5V or 11V and is further mentioned in Section 5.2.2 High-Side NFET Drivers of the BQ76952 Technical Reference Manual.

    You can disable the charge pump if the high-side NFET drivers will not be used in the application as well. How to do so is mentioned in the last paragraph of that section.

    We do NOT recommend using a resistor to pull CHG down to 0V as then you would short BAT to GND through the AFE. There is not anything you can configure in the software to have the CHG level be 0V.

    Best Regards,
    Alexis