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BQ76952: REG1 Issue in design

Darshil Dharod1
Prodigy 90 points
Part Number: BQ76952

Hi,

Hope you are doing well

We are using bq76952PFBR in our BMS and using REG1 to power MCU and a few other ICs (total load current ~8mA). The problem we are facing is that we are getting approx. 3.7 volt at REG1 with the preregulator enabled. The BREG voltage is 5.8 volt and REGIN voltage is 5.6 approximately. We also tried to change the REG1 voltage to lower value but it was still at 3.7 volt. We also verified the load at REG1 with external supply and no cells connected and we found it around 8mA.  

Also when we have the preregulator disabled, but cells connected and powering the Reg 1 using an external 3.3V, after removing the external 3.3V we still continue to have the same voltage at Reg1 (which should ideally go to 0).

  • 0
    TI__Mastermind 42060 points

    Hello Darshil,

    REGIN should be ~5.5-V, so that sounds about right. BREG controls the BJT in order to step-down the voltage to REGIN to ~5.5-V, so that seems okay too.

    I am confused as to what how you tested this. What do you mean there were no cells connected? The cells should be connected for proper operation of the IC, is there any issues when the cells are connected? REG1/REG2 can provide up-to 45-mA  load currents each. When powering REGIN externally, you should be supplying ~5.5-V into the REGIN pin in order to power up REG1/REG2. Make sure REG0 is disabled when using an external supply.

    What are your REG1/REG2 register settings? Were they programmed to be 3.3-V? See Section 6.3.2 REG1 and REG2 LDO Controls of the Technical Reference Manual. Confirm the registers are configured properly. Do remember to enable REG0 when using the pre-regulator circuit to power REGIN, see Section 6.3.1 Pre-Regulator Control of the Technical Reference Manual

    Share your schematic too, to confirm everything is okay, if the above did not fix your issue.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 90 points

    Hi Luis,

    Thanks for your answer.

    I will share our schematic and regulator register settings to you on personal message.

    Thanks,

    Darshil

  • 0 in reply to Darshil Dharod1
    TI__Mastermind 42060 points

    Hello Darshil,

    I sent you a friendship request, you can share those on private message.

    I will close this thread for now.

    Best Regards,

    Luis Hernandez Salomon