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BQ76942EVM: Charger Detecton

Rajendra Shenoy
Prodigy 40 points
Part Number: BQ76942EVM
Other Parts Discussed in Thread: BQ76942

Hi,

Wanted to check whether the EVM can be configured to detect the Charger and switch on the FET, so that the charging can happen without sending any commands?

Sincerely

Raj

  • 0
    TI__Mastermind 19650 points

    Hi Raj,

    The device should detect the charger being attached and automatically transition to NORMAL mode from either SLEEP or SHUTDOWN mode. The FETs should then turn on unless there is a fault or a host command that is keeping the FETs off.

    Can you share how you are testing this and your .gg config file?

    Regards,

    Max Verboncoeur 

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 40 points

    Hi Max,

    Thank you for your response.

    I haven't received my EVK yet for testing. Actually my end application is as below.

    1. The BQ76942 chip is interfaced with MCU

    2. when Battery pack is not in use, the FET will be switched off 

    3. For turning on the Battery output , switch will be used , which is detected by MCU and turns ON the FET / Battery pack 

    4. while in OFF mode, (FET OFF), can BQ76942, start charging without  any command issued by MCU. Or, is there any alert can be sensed to detect the charger insertion and MCU can switch on the FET for completing the charger path

    Sincerely,

    Raj

  • 0 in reply to Rajendra Shenoy
    TI__Mastermind 19650 points

    Hi Raj,

    A rising edge on the LD pin (which should be connected to PACK+ via a 10k) due to a charger being attached to the PACK terminals will automatically wake the device. If there is no fault keeping the FETs off, they should be able to turn on without a signal from the MCU.

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 40 points

    Hi Max,

    Thank you for our response.

    As Per me, the LD pin will go high in two situations:

    1. when the Battery is present and the FET turned ON (Discharge path)

    2. When Charger is attached.

    This is the exact problem for me. I want to test the Charging when I have kept the MOSFET OFF and charger Inserted. Can you please guide me any settings needs to be done in the EVK?

    Sincerely,

    Raj

  • 0 in reply to Rajendra Shenoy
    TI__Mastermind 19650 points

    Hi Raj,

    I'm not sure I fully understand what conditions you are trying to test under.

    If the MCU has commanded the FETs to turn off, then it will have to turn them back on with another command. If the device is in SLEEP mode or SHUTDOWN mode, and the MCU is not commanding the FETs to be off, when the charger voltage pulls LD up, the device will wake and enable the FETs autonomously.

    Is this not what you are seeing?

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 40 points

    Hi Max,

    Thank you for your response. Sorry for not being clear in my query.

    My end product requirement is as below:

    1. When the Battery pack is removed from the unit, the MOSFET should be OFF( Battery insert detection is separate circuit which indicates battery Used in product or out of product)

    2. As soon as Charger attached, I need to start Charging. for which the MOSFET to be turned ON. At this moment can I get some alert to MCU stating the charger attached?

    3. When the Charger is detached, the FET to be turned OFF

    4. Whole Idea is the Battery pack connector should not get Voltage when its not inserted in the end product 

    Hope above use case is clear.

    One more advice I would like to get from you is:

    I am using BQ7694202 part in my custom board. I am using REG1 as power to external MCU, which should be ON through out. Hope I will get 3.3V without any configuration

    Sincerely,

    Raj

  • 0 in reply to Rajendra Shenoy
    TI__Mastermind 19650 points

    Hi Raj,

    Since the MCU needs REG1 on to operate, SHUTDOWN mode won't be an option. Luckily DEEPSLEEP mode is similar to SHUTDOWN mode aside from the REGs still being enabled, however the only way to enter DEEPSLEEP is through a command from the MCU. This would require setting Settings:Configuration:Power Config [DPSLP_LDO] = 1 to keep the REGs on.

    The device includes a SLEEP mode where if the measured current falls below a user specified threshold, the device will automatically put the DSG FET into source-follower mode, and depending on the settings can also turn the CHG FET off.

    If the MCU is able to detect the battery being removed, it can send the command to enter DEEPSLEEP mode and both FETs will turn off.

    When the device detects a charger attached, it will automatically wake from DEEPSLEEP mode into NORMAL mode and re-enable both of the FETs. There is no automated alert for the device exiting DEEPSLEEP mode, but the MCU could monitor the 0x00: Control Status() [DEEPSLEEP] bit to determine if the device is in DEEPSLEEP mode or not.

    Again, the device would need the MCU to detect that the charger is dethatched and send the device into DEEPSLEEP, otherwise the device will just enter SLEEP mode when the measured current is below the threshold and not fully turn off the FETs.

    I strongly recommend reading through Section 7 of the TRM for more details on the different operational modes and their relevant settings.

    Regards,

    Max Verboncoeur

  • 0 in reply to Maxwell Verboncoeur
    Prodigy 40 points

    Hi Max,

    Thank you for the response. Will follow the details given. Will get back in case If I have further doubts.

    Sincerely

    Raj