• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 63 subscribers
  • Views 328 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25504 EVM problem

Aritz Estevez
Prodigy 65 points
Other Parts Discussed in Thread: BQ25504

Hello,

I was trying my BQ25504 EVM and everything seems to work like it is supposed. The battery start charging and stops when it is supposed. Once, when I was discharging the battery with a load and without VIN, I removed the load and the EVM didn't work correctly any-more. After that, every time I put voltage to VIN the VSTOR keep unchanged. It seems like the switch between VSTOR and VBAT is locked or isn't working well. Any idea of how unlock this state or if the chip is broken?

Thanks in advance for your help.

  • 0
    TI__Guru**** 167146 points

    Is the load attached to VBAT or VSTOR?  To what voltage did VBAT and/or VSTOR discharge?  If you completely discharge VSTOR and remove the battery, does the IC start working again?

  • 0 in reply to Jeff F
    Prodigy 65 points

    The load is attached to VSTOR. The IC works and give charge to VSTOR or VBAT, but the operation is not the specified in the datasheet.

  • 0 in reply to Aritz Estevez
    TI__Guru**** 167146 points

    There is a PFET between VSTOR and VBAT with source tied to VBAT so there is a diode that always allows current flow from VSTOR to VBAT.  PFET only turns on when VSTOR > VBAT_UV. 

  • 0 in reply to Jeff F
    TI__Guru**** 167146 points

     

    The switch between STOR and BAT initially closes for 50ms to charge the 4.7uF capacitor on STOR (CSTOR).  If the battery does not charge the capacitor above the user set VBAT_UV threshold, the switch opens but its body diode still allows current to flow from STOR to BAT. A load on STOR or BAT could significantly slow or even prevent CSTOR from charging above the 1.8V cold start threshold or the UV threshold.  Therefore, we recommend isolating the load from STOR or BAT with a switch that is controlled by VBAT_OK.

    The IC was designed with the expectation of a battery being connected only after the previous battery has been depleted or is damaged.  The switch between STOR and BAT will only close if the voltage on BAT and VSTOR is less than a few hundred millivolts just before the new battery is installed.  Therefore, before hot plugging a good battery, you should remove the old battery, power down the IC and discharge CSTOR and the battery capacitor (CBAT).  

  • 0 in reply to Jeff F
    Prodigy 65 points

    Thank you for your reply.

    I have another evaluation board that also fails. After a reconfiguration of UV and OV resistances, we returned to the previous state. We then put the same values that cames with the factory specifications and it seems that the UV is equal to the OV (or very similar). We have checked the resistances several times. Did anyone suspect where could be the mistake? 

    Thank you in advance.