• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 64 subscribers
  • Views 93 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

Original question:

BQ76942: CUDEP protection, FET fail, FUSE and Permanent Fail

BQ76942: CUDEP protection

Attila Dányádi
Prodigy 100 points
Part Number: BQ76942

Hy Matt,

I have to reopen this issue regarding to CUDEP protection.

I choosed your first suggestion:

"If you are planning to program OTP in production, then maybe you can set PF_EN = 0 in OTP and then send the PF_ENABLE() command from the microcontroller at power-up. This way the permanent fail will not cause an issue while connecting the cells."

In this case CUDEP is not activated. The device wakes up from shutdown mode by charge detect with the settings of Manufacturing Status.PF_EN = 0 from OTP.

Sending the PF_ENABLE() command is late.

In case of PF_EN = 1 in OTP the CUDEP is activated, but it causes to impossible to assembly the battery pack without risky tricks.

If I remember well BAT and VSS pins should connected (power up) before connecting the cell inputs. Am I right?

I really need a good idea, how to implement recharge protection when a cell is under 2Volt.

BR,

Attila

does_not_work.gg.csvworks.gg.csv

  • 0
    TI__Guru* 78003 points

    Hi Attila,

    So, the issue with the first case is that charging is allowed for a time while the PF_ENABLE() command is sent and executed? In this case, would it be better to keep the CHG FET disabled until the microcontroller determines that conditions are okay? This could be accomplished in different ways. For example:

    • FET_EN can be set to 0 in the Mfg Init Status register. The microcontroller can send the PF_ENABLE() command then the FET_ENABLE() command. This could be a little slow, but it prevents charging until it is verified there is no PF condition.
    • The CFETOFF pin can be configured to control the CHG FET and the microcontroller could hold this pin until it determines it is safe to allow charging. For example, it could read the Safety Alert registers to make sure that under-voltage conditions are not triggered and then release CFETOFF. Or it could read the cell voltages and make a decision. 

    Regards,

    Matt