• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 658 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.

BQ27742-G1: Disconnecting CHG & DSG FET simultaneously by firmware

neri naveh
Prodigy 40 points
Part Number: BQ27742-G1
Other Parts Discussed in Thread: BQSTUDIO

We need an option to disconnect our battery  pack from the device for long periods using firmware (we do need that the disconnected cell will not charge, even if charger is connected and will not discharge till firmware will enabled it again). We have tried two methods in order to open CHG & DSG external FETs , both were failed:

1. Using the FETtest register – From some reason , when applying 0x0083 to 0x73,0x74 register  only one FET is being closed – sometimes it  is the CHG and sometimes it’s the DSG - It may depend on cells charge/discharge status, if yes – how can I permanently disconnect the two FET , together?(no matter what is the cell current direction when disconnecting it).

2. Another option we have tried is to set OT conditions below the current temperature reading (both for charge and discharge) , using the BQstudio we have changed the relevant values in the flash , reset the device but still FET were closed and no OTC flag was raised (all other device configuration are at default).

Did we missed something? Any other option for such a control over the transistors?

  • 0
    TI__Guru* 76230 points

    Hi Neri

    -The fet commands are not put in place to turn the fets off while the chip is deployed. It is for testing purpose to verify the functionality of the fets. see TRM

    - For this second method, did you try power cycling the device? This is not a viable solution either.

    You could either sent the shutdown command to shut the device off or you could carry out the disconnection using external components and your host.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 40 points
    Thanks
    1- Currently we do try to do this for testing purpose, could find in TRM why writing 0x0083 to FETtest and executing it by putting 0x24 to control register will not always open both registers
    2. shutdown is fine be -reconnecting the charger will re enable the devcie ... any option to prevet it from being turn on again
  • 0 in reply to neri naveh
    TI__Guru* 76230 points
    -do you have IT enabled?- you are not supposed to turn it on.. I do not see anywhere 0x0083 is mentioned in the trm?
    -yes applying a charger wakes the device on and the fets as well
  • 0 in reply to Onyx Ahiakwo
    Prodigy 40 points
    According to the TRM (pages 55-56) writing 0x0083 to FETtest():(0x73-0x74) shell open CHG,DSG and put RECEN in firmware control mode .The command is verified by putting 0X2 to the CHKSUM bits. My question is what other conditions are controlling the FET open/close as the same command (0x83) open different transistor each time. (somtimes it's open the CHR and somtimes the DSG)
    Thanks