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TDA4VM: How to control PMIC-B LDO1 output from 3.3V(bypass mode) to 1.8V(LDO mode) for SD switch in J721E EVM?

Part Number: TDA4VM

Hi Expert,

How to control PMIC-B LDO1 output from 3.3V(bypass mode) to 1.8V(LDO mode)?

We know that the voltage switch is for switch SD voltage work status from initialization to normal work status.

According to below diagram, it seems that there is a MMC1 IO which can control TPS659411 SD voltage through GPIO2, but from schematic, GPIO2 is only a test point, How to control PMIC-B LDO1 output from 3.3V(bypass mode) to 1.8V(LDO mode) in J721E EVM?

  • Hello,

         Please confirm in the schematic which regulator is providing the SD voltage.  If R464 is not installed and R465 is installed the voltage is coming from U101.

    Once you make the above connection to the TPS659411-Q1 device, then you can either blue-wire a connection (SEL_SDIO_3V3_1V8n) to the testpoint or resistor.  Alternatively you can write to the PMIC via I2C to change the LDO1 to either bypass or LDO mode.

    Regards,

    Chris

  • Hi Expert,

    I did a test: connect GND to TP109(PMIC-B’s GPIO2)and found that TP137(PMIC-B’s LDO1) switched from 3.3V to 1.8V.

    Then connect SEL_SDIO_3V3_1V8n to TP109(PMIC-B’s GPIO2), and the CPU still doesn't start properly.

    Finally, the power-on timing of TP137(PMIC-B’s LDO1) and TP166(U101s output) is captured with an oscilloscope. The green color in the figure indicates TP137 and the yellow indicates TP166.

    Their timing is almost consistent, so why can't PMIC-B’s LDO1 start the CPU properly?

     

     

     

  • Hello,

    When you perform the transition on the PMIC-B’s LDO1, does the nINT signal change?  (is there an error during the transition?)

    Regards,
    Chris

  • Hi Expert,

    After switching the voltage again, I measured that the nINT level was pulled down. The output of the other power rails is normal, where did the error occur?

  • Hello,

    I think you are seeing an error in the LDO voltage monitor.  How quickly does the rail transition from bypass to LDO mode?  How much capacitance is on the LDO?  Can you lower the capacitance and determine if the error goes away?  Also, you should be able to read the interrupts to see why the error occured.  

    Regards,

    Chris