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BQ76952: FET Control using FET Test Mode

Vaithieswaran S
Prodigy 50 points

Part Number: BQ76952

Hi All,

I would like to control separately the FET in both PDSG, PCHG  , CHG, DSG pins through command .

Kindly share the procedure in order to control the individual FET's. If you are mentioning the TEST mode command. If we enable the FET through TEST mode command will the protections get disabled?

  • 0
    TI__Guru* 81035 points

    Hi,

    Yes, you can control these FETs individually through the FET Test mode, but we normally do not recommend FET Test mode for normal operation since it was not originally intended for this. The protections and autonomous recovery are still active in FET Test mode, but there are some other features are not available:

    • The DSG_PDSG_OFF(), CHG_PCHG_OFF(), ALL_FETS_ON(), ALL_FETS_OFF(), and FET_CONTROL() commands should not be used while in FET Test mode. Instead, you must use the DSGTEST(), CHGTEST(), PDSGTEST(), PCHGTEST() commands.
    • The device will not autonomously transition between precharge mode (PCHG FET enabled, CHG FET disabled) and charge mode (PCHG FET disabled, CHG FET enabled). Similarly, the device will not autonomously transition between predischarge mode (PDSG FET enabled, DSG FET disabled) and discharge mode (PDSG FET disabled, DSG FET enabled).
    • The device will no longer autonomously control the CHG FET based upon the FET Options[SLEEPCHG] setting. If the user desires the CHG FET to be disabled in SLEEP mode, the user must disable it using the CHGTEST() command.
    • The FET test commands cannot be used when the device is SEALED.

    The FET Test mode may meet your needs, but I advise careful testing to ensure the behavior is well understood since it is different than the normal mode.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 50 points

    Hi Matt,

    We would like to use Precharge path(PDSG,PCHG) and Main path (CHG and DSG) FETs based on current. In view of this, we would like to Turn ON or OFF the PDSG and PCHG FET in normal mode. Could you please help to share the procedure on how to switchover between prepath and Main path FETs in run-time ?

  • 0 in reply to Vaithieswaran S
    TI__Mastermind 42310 points

    Hello Vaithieswaran,

    There are holidays this week in the USA and Matt is on vacation for the week. 

    I don't believe there is a good way to control the PDSG/PCHG based on just current during normal operation. If using FET TEST mode, maybe you could do so if controlled through a MCU. But it is advised, as Matt mentioned, to be careful.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 50 points

    Hi Luis / Matt,

    Kindly let us know how to control the PDSG / PCHG FETs and DSG / CHG FETs independently in the "Normal mode". Is there any sequence of commands to be followed?  We may choose to handle these FETs based on our application needs in run-time.

  • 0 in reply to Vaithieswaran S
    TI__Mastermind 42310 points

    Hello Vaithieswaran,

    It would not be possible to control the PDSG/PCHG FETs independently in normal mode. However, it would be possible to control the DSG/CHG FETs through the commands DSG_PDSG_OFF(), CHG_PCHG_OFF(), ALL_FETS_ON(), ALL_FETS_OFF(), and FET_CONTROL(). 

    You can see the last couple of responses from this older e2e thread for guidence: e2e.ti.com/.../bq76942-write-fet_control-under-i2c

    Best Regards,

    Luis Hernandez Salomon