• State TI Thinks Resolved
  • Locked Locked
  • Replies 10 replies
  • Answers 1 answer
  • Subscribers 65 subscribers
  • Views 592 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.

BQ76952: BQ76952 data reading abnormality and DCHG abnormal shutdown

Star Xu
Genius 9645 points
Part Number: BQ76952

Hi

The customer has some problems when testing BQ76952.

1, When reading current and voltage, the read data is abnormal .

The following is the collected cell voltage:

3328mV = 0x0D00

3072mV= 0x0C00

It is speculated that when the voltage changes from 0x0D00 to 0x0CFF, when the MCU reads the low byte (0x00), the high byte data changes from 0x0D to 0x0C, causing the data read by the MCU to be 0x0C00, which is different from the actual value 0x0CFF. How to solve this problem?

2, When using DCHG and DDSG to control the MOS, when DDSG is turned on, DCHG will be disconnected (the FET_CONTROL subcommand (0x0097) is used). Is there any solution to this problem?

As shown in the figure below, when DCHG is turned on, turning on DDSG will cause DCHG to turn off

Please help check it.

Thanks

Star

  • 0
    TI__Mastermind 25750 points

    Hi Star,

    1. Is the customer making sure that they are waiting long enough for the device to load the cell voltage data into the transfer buffer? If they try to read the data too fast they might get bad data out, similar to what they are seeing.

    2. Do you have the customer's settings and what they are sending with the FET Control subcommand?

    Regards,

    Max Verboncoeur

  • 0
    TI__Mastermind 42060 points

    Hello Star,

    Are they using block reads to read the cell voltages? Using block reads should avoid having issues if the cause is due to reading the different bytes of cell voltages at different times. 

    DCHG/DDSG should not be used with FET_CONTROL. See this older E2E:

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Genius 9645 points

    Hi Luis

    Thanks for your reply.

    1, Parameter settings: DCHG to DCHG Mode and DDSG pin to DDSG Mode.

    DCHG Pin Config（Addr0x9301) = 0xAA.

    DDSG Pin Config（Addr0x9302) = 0xAA.

    FET Options (Addr0x9308) = 0x2E.

    DCHG and DDSG can be controlled through FETControl (Subcommand 0x0097). The problem is that when one of them is closed (such as DCHG is closed), closing the other (such as DDSG) will cause the control pin that is already closed to be briefly disconnected.

    2, FET Control command content:

    Read the FET Status() (cmd:0x7F) status as 0x61 (DDCHGbit = 1). At this time, write the value 0x00 (CHG_OFFbit = 0, DSG_OFF = 0) to FET_CONTROL() (subCMD:0x0097). Normally DDSG should be closed and DCHG status should remain unchanged.

    After writing, DCHG is first turned off for about 100ms (waveform diagram posted above), and then DCHG and DDSG are turned on together.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Mastermind 42060 points

    Hello Star,

    As I said, they should not be using the FET_CONTROL commands with the digital pins DDSG/DCHG.

    If they want to control the FET's turn-off, they should use the CFETOFF and DFETOFF pins instead.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 30 points

    Hi Luis,

     Thank you for your reply, we will take note of this.

     However, for BQ7695204, the CFETOFF pin is default for SPI SEN mode. Is there any other solutions that can use both SPI communication and controlling MOSFET?(For our products' MOSFET controlling only needs a 5v -level's signal.)

  • 0 in reply to Zhengxi Pan
    TI__Mastermind 42060 points

    Hello Zhengxi,

    Could you could use the DFETOFF pin (configured as BOTHOFF)? Which would mean that both FETs would turn-off when the DFETOFF pin is asserted.

    Any reason why you would not want the AFE to do autonomous control?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 30 points

    Hi Luis，

    For our design, the CHG MOSFET and DSG MOSFET should  be controlled independently. The autonomous MOSFET conrtolling of the AFE is commonly used to do the sencond safety level.

    Is there any other solution that can be implemented?

    Best Regards,

    Zhengxi Pan

  • 0 in reply to Zhengxi Pan
    TI__Mastermind 42060 points

    Hello Zhengxi,

    It could be possible to use logic gates along side the DDSG/DCHG pins in order to essentially turn-off the FETs whenever the MCU wants it to. This would also allow autonomous control by the bq76952.

    This would be a board-level solution.

    It could be possible to use the TEST commands, but these have not been fully characterized/tested.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 30 points

    Hi Luis,

    Would it be possible to use the PCHG and PDSG as the Charge/Discharge Mosfet control signal. Which means it could be controlled to turn off the mosfet by AFE itself when it's protection tigerred, and also be controlled on/off by the MCU when need。

    Best Regards,

    Zhengxi

  • 0 in reply to Zhengxi Pan
    TI__Mastermind 42060 points

    Hello Zhengxi,

    No, that is not possible. The PCHG/PDSG drivers are high-side P-FET drivers, as such to turn-on FETs they draw current into the pin.

    It can also be possible to use MOSFET switches to control if the FET is on or OFF through the micro-controller, instead of using logic gates to control the low-side drivers.

    Best Regards,

    Luis Hernandez Salomon