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[Urgent] Appear the unintended voltage on ANA_LDO

Kaka
Guru 24520 points

Hi,

Please provide your advices to us.

[Phenomenon]

Appear the unintended voltage(Approximately 0.4V) on ANA_LDO during RTC-only mode.

I summarized this phenomenon to Power point file.

Please check this one.

Can you guess where this 0.4V has occurred?

* We would like to know why this unintended voltage has appeared.

If you have any questions, please let me know.

Best regards.

Kaka

7382.ANA_LDO_issue.pptx

  • 0
    TI__Mastermind 23785 points

    Kaka-san,

    The ANA_LDOO pin is intended for the VDDA_ANA and VDDA_PLL pins to provide a regulated 1.3 V to the SAR ADC, Power Management Circuits and System PLL. USB_LDOO is intended for the USB_VDD1P3 and USB_VDDA1P3 pins to provide power to portions of the USB. The C5534N supports the USB_LDOO while C5532N does not.

    What is the reason for not using C5534N?

    The 0.4V seen on ANA_LDO when JP15 pin2 is connected to JP16(1-2) is from USB_VDD_IN (JP15 pin2). I saw a 0.6V on USB_VDD_IN by itself. I am still checking why this voltage exists. As you have seen, there is 0V on ANA_LDO when it is not unconnected to USB_VDD_IN at RTC-only mode.

    Regards.

  • 0 in reply to Steve Tsang
    Guru 24520 points

    Hi Steve,

    Thank you for your confirming and support.

    The reason why they have used the C5532N for their application is the cost.  The device cost of C5534N is higher than C5532N.

    Regarding to customer,