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BQ76952: Some questions about 76952

Tan Haitao
Prodigy 210 points
Part Number: BQ76952

1.do I need to send check sum when I send a subcommand,I see  <<BQ76952 Software Development Guide >> read  DEVICE_NUMBER - 0x0001 doesn't send the checksum

2.do I need to send enter  CONFIG_UPDATE mode when I send a subcommand, some times I send subcommd,it does't work

3.how long does the ic need to power on(Initialization time),what would happen when i communicate during this time?

4.The measurement loop is 63ms(or 31.5ms when fast),but I read cell volt every 10ms, the cell volt would change every time,how does that happen?

5.I sometimes found strange phenomenon，like can't communicate, or read back wrong data, the BQ76952 is stable now?

  • 0
    TI__Guru* 81034 points

    Hi Tan,

    1. No, you do not need to send a check sum when reading the Device Number because you are not writing any data. See the example in the Software Development Guide for reference.

    2. No, CONFIG_UPDATE mode is only needed for writing to the RAM registers and for programming the OTP.

    3. Section 16.4 of the datasheet shows the typical startup timing for the device. It is best to wait until the regulators are up, so around 20ms.

    4. The cell voltages should only change each time through the measurement loop.

    5. Yes, the device should be stable. The host should support clock stretching - the BQ76952 will hold the clock low if it needs more time to send the data. For the subcommands that use 0x3E, you should wait a little longer before reading data from 0x40. The typical times of the subcommands are listed in Table 9-2 of the TRM. Many users wait 2ms for these commands because it gives plenty of margin for all of the commands.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 210 points

    Thanks for your answer

    1.On datasheet, "The checksum is calculated over 0x3E, 0x3F, and the buffer data ",so is it better to send checksum,even don't have any data.I think the subcommnd also need to check,just in my view.

    2.I will check other things