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BQ76905: Enquire about Initial state of the BMS Chip

Po Yang Khor
Prodigy 110 points
Part Number: BQ76905

Tool/software:

My Schematic shown as below.

I would like to ask about the datasheet 7.4.7 Standalone Versus Host Interface(pg 29). From this section, I know that this chip which able to use standalone mode. I am using standalone mode to activate the chip, but I have facing some issue. In 7.8.1 Overview of Operational Modes, there are 4 modes. Based on this section, I obtain deep sleep mode results as REGOUT LDO is 3.3V;CHG is 0.5V and DSG is 0V through multimeter.

1. May I know what is the actual initial state of this IC as I cant found or miss out in the datasheet? 

2. Is it necessary to include the circuit shown as below to let deep sleep mode become normal mode if using standalone mode to activate it as I did not include this part in my circuit which shown in the pg 43 datasheet.

3. If no included the circuit that shown in question 2, so need to have at least TS pin or VC0 connect to MCU digital pin for wake up(for shutdown mode)?

Thanks in advance.

  • 0
    TI__Expert 5090 points

    Hi Po,

    To use this device in standalone (meaning no MCU in system) mode, you either need to configure it on your production line and let it stay powered permanently, or if your business volume is sufficient TI can preprogram a version already configured for you.  But the standard catalog part cannot be used in standalone mode without following one of these approaches.

    Your schematic shows an MCU in the system, so do you really need standalone mode?

    The device will not enter DEEPSLEEP unless it is directed by a host communicating over I2C.  From your description, I assume you have never configured the device.  The default settings mean the device will start up in NORMAL mode but keeping the FETs disabled, then will transition into SLEEP mode.  The part doesn't need to be wakened from SHUTDOWN unless you sent it into SHUTDOWN mode by I2C command, or you configured it to automatically go into SHUTDOWN upon a certain condition, such as a very low cell or stack voltage.

    Thanks,

    Terry