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AM3356: Will VDD_CORE exceed maximum current?

g.f.
Guru 15510 points
Part Number: AM3356
Other Parts Discussed in Thread: TPS65910

Hi,

My customer are using AM3356 and TPS65910A31A1 as a power supply of AM3356.
And they are having some issue on the power line VDD2(PMIC) - VDD_CORE(AM3356).
We don't know the cause yet, but the current of VDD_CORE fluctuates from 0mA to about 600mA in 10us period.
(0mA -> 600mA -> 0mA -> 600mA -> -----)

In the datasheet of AM335x, it's written as that VDD_CORE current range is 400mA(maximum).
Will VDD_CORE ever exceed this 400mA?

best regards,
g.f.

  • 0
    TI__Prodigy 640 points

    Hi,

    Thank you for reaching out.


    Please help me with the below details
    1.Could you let me know that this current fluctuation is observed in custom board or EVM.
    2.Please confirm if this behavior is seen in multiple boards.
    3. Also, kindly share the schematic connections between PMIC and VDD_CORE for review.

    Regards,
    Kalyan.

  • 0 in reply to Kalyan Gajjala
    Guru 15510 points

    Hi Kalyan,

    Thank you for the reply.


    >Please help me with the below details
    >1.Could you let me know that this current fluctuation is observed in custom board or EVM.

    It's observed in custom board.

    >2.Please confirm if this behavior is seen in multiple boards.

    This behavior is seen in 20-30 boards per 100 boards.

    >3. Also, kindly share the schematic connections between PMIC and VDD_CORE for review.

    The power schematic of our customer's board was designed by refering to AM335x Starter Kit board.
    I will attach the schematic of Starter Kit board.

    best regards,
    g.f.

    AM3356_TPS65910A31_connection.pdf

  • 0 in reply to g.f.
    TI__Guru** 123748 points

    Hello G.F, 

    Thank you for the inputs.

    If customer has used the same circuit the cause of failure could be the components, board design or manufacturing.

    I am not sue if we could provide any additional suggestions based on the AM335x Starter Kit board schematics since the boards are working.

    Can you please suggest to check if the components used are same and the board design follows the AM335x Starter Kit board.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Guru 15510 points

    Hi Sreenivasa,

    Thank you for the reply.
    I understood but let me ask a few more questions.

    Q1.
    If there are no problem in the device AM335x, the board design, etc..,
    the current will never exceed max 400mA, is it correct?

    Our customer are using TI Linux SDK and have following questions:
    Q2.
    In default, the u-boot configuring the TPS65910 register via I2C to update VDD_MPU and VDD_CORE voltage.
    u-boot does not set the VDDx_REG register value ILMAX of TPS65910, but does the user need to add this setting to u-boot?

    Q3.
    And what value should VDD2_REG register value ILMAX be set for AM335x?
    When set to 0, the maximum load current of VDDx will be 1.0[A],
    and when set to 1, the maximum load current of VDD2 will be 1.5[A].

    Q4.
    VDD2(TPS65910) are connected to VDD_CORE which maximum current is 400mA,
    so I guess VDD2 register value ILMAX should be set to 0(max 1.0[A]), is it correct?
    If this is correct, I think there are no need to configure ILMAX in u-boot because default value of ILMAX is 0.
    How do you think?

    By the way, the reason why I'm asking such questions(Q2-Q4) is because I heard that this issue(current fluctuation of VDD_CORE) can be solved by setting ILMAX of VDD2 Register to 1 (1.5[A]).

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru** 123748 points

    Hello G.F, 

    Thank you for the inputs. Please refer below answers

    Q1.
    If there are no problem in the device AM335x, the board design, etc..,
    the current will never exceed max 400mA, is it correct?

    You understanding is correct 

    Q2...Q4 depend on the component selection, layout etc. Customer can set the current based on the performance.

    By the way, the reason why I'm asking such questions(Q2-Q4) is because I heard that this issue(current fluctuation of VDD_CORE) can be solved by setting ILMAX of VDD2 Register to 1 (1.5[A]).

    As i mentioned this could be due to component selection, design, layout etc.

    Please ask customer to review the design and compare with the EVM.

    Let me know if you have any other thoughts.

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Guru 15510 points

    Hi Sreenivasa,

    Thank you for replying quickly.

    Okay, I will suggest to my customer to review the design and comparing with the EVM.

    Regardless of this issue, can you tell me whether the user need to setup
    the TPS65910 VDDx_REG register value [ILMAX] in the u-boot usually or not?

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru** 123748 points

    Hello G.F, 

    Thank you for the note and appreciate your coordination with customer on the issue.

    Regardless of this issue, can you tell me whether the user need to setup the TPS65910 VDDx_REG register value [ILMAX] in the u-boot usually or not?

    Good question. This would be best answered by an U-BOOT expert.

    Would you mind creating a new thread with title " TPS65910 VDDx_REG  - UBOOT configuration" to get wider support. This will help future users also.

    Thank you for the help.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Guru 15510 points

    Hi Sreenivasa,

    Thank you for the reply.

    I created new thread as follow:
    e2e.ti.com/.../am3356-tps65910-vddx_reg---uboot-configuration

    I would like to wait for the response from u-boot expert.

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru** 123748 points

    Hello G.F, 

    Thank you for the help and appreciate.

    I will also look out for the response from u-boot expert.

    I will close the thread. Thank you and have a good day.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Guru 15510 points

    Hi Sreenivasa,

    Thank you so much for all the support what you did to me.

    best regards,
    g.f.

  • 0 in reply to g.f.
    TI__Guru** 123748 points

    Hello G.F, 

    Noted, happy to support and Thank you. 

    Regards,

    Sreenivasa