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BQ51051B: Stop Wireless Charger operation using pins from BQ28Z620 without I2C and MCU intermediation

Fernando G.
Prodigy 70 points
Part Number: BQ51051B

Tool/software:

Hi TI team,

we are using the BQ51051B wireless charger IC on a design where we were measuring the temperature in a custom way to only allow charging on a temperature interval. Now, we would like to substitute this custom circuitry for a BQ28Z640 fuel gauge to control temperature but also getting some SoC and SoH parameters. 

We have been reviewing the recommended fuel gauge schematics, and all of them points to use a back to back MOSFET configuration to unplug the power line in case any alarm is triggered, by driving CHG and DSG pins. We would like to avoid the use of these two extra components and to connect any of these CHG and DSG directly to the AD pin of the BQ51051B battery charger so that the charghing is stopped.



Another option could be to use the wireless charger TS/CTRL or EN2 pins to drive the charging operation with the help of a MOSFET or something if required, but we see this much more complicated or required external circuitry. Our idea is to need the less components we can and to make the charging process independent from a microcontroller.

During the docs review, we are only clear that, wireless charger CHG should be pull-down driven but not many information regarding the fuel gauge CHG/DSG internal schematic, so we do not know if these configuration proposed on the image could be possible. We also posted here and another TI colleague pointed us out to here to the BQ51051B experts.

Any information you could provided, will be welcome.

Regards,

  • 0
    TI__Guru** 104010 points

    Hello Fernando,

    We are looking into your questions and will respond by the end of today.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Guru 70106 points

    Hi Fernando

    I recommend keeping the back to back MOSFETs to isolate the battery cell.   This will prevent a number of potentially harmful conditions such as over discharge and other.

    Also the connection for the BQ51051B OUT should be at PACK+ node.

    The AD pin can be used as a logic input to disable the charger.

  • 0 in reply to Bill Johns
    Prodigy 70 points

    Hi Bill,

    thanks for answering. Our client does not need this back to back circuit because they isolate the battery in another stage. We are testing the BQ51051B IC and see AD pin is not the one we need because of the operation it makes with the charger. We believe the only possibility is using TS/CTRL pin.

    Any guide or recommendation about how to cut the WC charging process using TS/CTRL externally (with or without a transistor) would be appreciated.

    Regards,

    Fernando.

  • +1 in reply to Fernando G.
    TI__Guru 70106 points

    Hi Fernando

    Fernando G. said:
    Any guide or recommendation about how to cut the WC charging process using TS/CTRL externally (with or without a transistor) would be appreciated.

    Pulling TS/CTRL High will send End Power Transfer and turn off the transmitter.   Note that high for TS/CTRL is 0.2V to 5V.