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AM5706: PMIC shutdown

shigehiro tsuda
Mastermind 9490 points
Part Number: AM5706
Other Parts Discussed in Thread: LM5141, TPS65916

Hi,

Our customer is designing with reference to the following references design.

www.ti.com/.../tidrts1.pdf

AM5706 has the following errata.
i862 Reset Should Use PORz

The workaround in the above reference seems to have selected Implementation 1, but there is the following description.

The side effects/risks of this implementation include:
This implementation does not allow software to shutdown the PMIC outputs that power the SoC.
Only the PMIC RESET_IN can shutdown the PMIC outputs while POWERHOLD is pulled high.

In the TPS659163 used, RESET_IN and NRESWARM are commonly assigned to the GPIO_1 pin.
How is it shutdown?

Best Regards,
Shigehiro Tsuda

  • 0
    TI__Genius 13567 points

    In the reference design the PMIC power state is controlled by "POWERHOLD" input. So this is selected with SW2 on page 24 of the schematic. 

  • 0 in reply to Ahmad_Rashed
    Mastermind 9490 points

    Hi Ahmad,

    Thank you for quick reply.

    I understand that only the powerhold pin can be controlled in the reference design.

    Is there a good idea to run the PMIC power-down sequence when the main power is off?
    Is it necessary to detect the level of the main power supply threshold voltage, control the powerhold pin,
    and turn off the main power supply completely after the PMIC power-down sequence is complete?

    Best Regards,
    Shigehiro Tsuda

  • 0 in reply to shigehiro tsuda
    TI__Genius 13567 points

    Is there a good idea to run the PMIC power-down sequence when the main power is off?


    Yes the voltage supervisors on page 23 will monitor VBAT and initiate the power down sequence on the PMIC. This allows the PMIC to shutdown properly be before the LM5141 shuts down. If you wait for the LM5141 PG signal then this might be too late. The LM5141 will shut down and the PMIC may not have time to shutdown properly.

    Is it necessary to detect the level of the main power supply threshold voltage, control the powerhold pin, and turn off the main power supply completely after the PMIC power-down sequence is complete?


    Do you mean disable the supplies between main input and the PMIC such as the LM5141? I'm not sure but that is likely not necessary and up to the system designer.

  • 0 in reply to Ahmad_Rashed
    Mastermind 9490 points

    Hi Ahmad,

    Thank you for quick reply.
    I understand that this reference design is the schematic that main power is turned off by the LM5141 control after the TPS65916 shutdown sequence is complete.

    Best Regards,
    Shigehiro Tsuda