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BQ76952: Use DDSG or DCHG as signal input to control mos to achieve the short protect?

Nan Zhang
Intellectual 1895 points
Part Number: BQ76952

Hi team,

     The customers want to use DCHG or DDSG of BQ76952 as a signal to control the high side MOS to achieve short protect When SRP and SPN pin measure the short. Does our BQ76952 meet their needs?

     If yes, how to set the registers to achieve that?

  • 0
    TI__Mastermind 27321 points

    Hello Nan,

    The device can do this autonomously. Please see below. If customer needs help configuring the registers, please let me know. 



    Regards,
    Jose Couso




  • 0 in reply to Jose Couso
    TI__Intellectual 1895 points

    Hi Jose,

         Thanks for your reply.

         Could you please share the configuring the registers? 

    YOURS 

    NAN

  • 0 in reply to Nan Zhang
    TI__Mastermind 27321 points

    Hi Nan,

    To achieve the Short Circuit in Discharge Protection (SCD), the customer will need to look at Section 5.2.6 of the Technical Reference Manual (TRM). 

    The short circuit protection is configured according to the sense resistor being used and depending at what current it is desired to trigger SCD. The device will monitor the differential voltage across  SRN and SRP  pins and triggers a SCD alert or fault when the voltage exceeds a programmable threshold.

    For instance, say the customer is using a 1mOhm sense resistor and wants to trigger SCD at 10A. The Protections: SCD: Threshold will need to be set to 10mV. This is all explained in the section 5.2.6

    After configuring SCD in protections, then customer will need to configure the CHG or DSG FET (can be both) to turn OFF during a SCD fault. To achieve this, the Settings: Protection: CHG FET Protections A[SCD] bit must be set. Same applies for Settings: Protection: DSG FET Protections A[SCD] 

    Note: For the fastest SCD response, the CHG FET Protections A and DSG FET Protections A  need to be set as below.



    Remember that for fully autonomous, the Settings:Manufacturing:Mfg Status Init[FET_EN] configuration bit must be set.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    TI__Intellectual 1895 points

    Hi Jose,

        After talking with customers, they still want to use DDSG to control low side. The document you provided is to use DSG or CHG.  Do you have idea that we can make DDSG to follow DSG when SRN and SRP find short?

    YOURS

    NAN

  • 0 in reply to Nan Zhang
    TI__Mastermind 27321 points

    Hello Nan,

    This makes more sense now. In the picture of the first post, I saw high side driver. 

    For low side, the Digital DSG and CHG pins are used to drive the low side driver. 

    The DDSG and DCHG pins can follow the state of the DSG and CHG pins respectively. This can be achieved by configuring the DDSG Pin Config and the DCHG Pin Config registers. How to configure these registers is discussed in Section 6.4 Multifunction Pin Controls of the TRM.


    Note:     You still want to have Settings: Protection: CHG FET Protections A and Settings: Protection: DSG FET Protections A registers configured as the Digital DSG and CHG will follow the state of FETs.

    This E2E thread also helps with some configuration details. 

    As for reference design, we do have one https://www.ti.com/tool/TIDA-010216 

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    TI__Intellectual 1895 points

    Hi Jose,

          Sorry for wrong the picture. I read the TRM, the DDSG or DCHG need to be set to register to change low or high manually. The time changing the registers would be so long when  the short is measured. We see that the DSG or CHG has internal logic on SRN and SRP testing the short, which is internal hardware protection faster than setting registers. So can set the DDSG or DCHG get link with the SRN and SRP measuring?

    YOURS

    NAN 

  • 0 in reply to Nan Zhang
    TI__Mastermind 27321 points

    Hello Nan,

    Yes, both DDSG and DCHG should be able to follow DSG and CHG FETs instantly. 

    Regards,
    Jose Couso 

  • 0 in reply to Jose Couso
    TI__Intellectual 1895 points

    Hi Jose,

         The customer has set the registers as we discussed before. They found that the DDSG followed the DSG.But when RSN and RSP find the short, the DSG was pulled up first, and after t 30-50ms , DDSG followed the DSG. Time of following is quite long the the short protection. I remembered that the DDSG would follow DSG within 1us. Is there other registers need to set?

    The DDSG is green and the DSG is yellow.

      But when the power up the BQ76952, the DDSG follow the DSG within serval seconds.

    YOURS

    NAN

  • 0 in reply to Nan Zhang
    TI__Mastermind 27321 points

    Hello NAN,

    Do they have the CHG FET Protections A and DSG FET Protections A registers set to the below description? The device will take up to 250 ms if they do not do this.



    Regards,
    Jose Couso