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BQ76952: Chip I2C response only on 5-13V

RUSHAB SHINGI
Prodigy 100 points
Part Number: BQ76952

Hello All,
I have a custom board for BQ76952PFBR


sharing image of the  schematic 
I have already soldered 33E, 100nF filters on Sense voltage input pin VC16-VC0
also, I have an external voltage divider on all the VC pins to emulate the behaviors of the cells
I can measure 1.8V on REG18
REG1 and REG2 are not used hence REGIN and BREG are connected to GND
TS2 pin is also connected to GND to avoid the chip to shut down (No response on I2C when TS2 is floating and it measures 1.4V on floating )
I2C lines are connected to the controller with 10K pullups on 3V3
In the above conditions, The chip responds on I2C on stack voltage from 5.6V to 13V (Sometimes 18V)
After 13-18V the chip stops responding on the I2C lines however 1.8V is still present on REG18

Also, can it be something related to OTP programming
because the chip can be programmed in OTP mode when stack voltage is between 10 to 12V
Thanks in advance
Rushab

  • 0
    TI__Guru 54715 points

    Hi Rushab,

    TS2 pulled low will wake the part.  The part is awake since you are measuring REG18 at 1.8V.  The BQ76952 should work up to 85V although you want to leave room for the charge pump voltage.  If it stops working reliably above 13V applied, check for a ground shift between the BQ76952 and the MCU board as the voltage increases. 

    It should not be related to OTP programming since you do not mention it.  Various versions are available, but you seem to have an I2C version since you can talk to it.  Unless you change the interface the I2C should continue to work. 

    Please check ground differences and power supply noise at higher voltages.