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TDA4VM: RTC source from PMIC

Jimmy Hsueh
Prodigy 130 points
Part Number: TDA4VM
Other Parts Discussed in Thread: TPS6594-Q1,

Hi,

From the EVM we know that there do needs an external RTC chip for TDA4. (Through I2C interface)

But it seems the PMIC TPS6594-Q1 has this RTC function inside either.(With both VBACKUP and OSC32K pins)

So my question is could the PMIC support TDA4 with backup RTC? We're considering to remove the extra one.

Thanks.

Jimmy Hsueh

  • 0
    TI__Intellectual 1170 points

    Hi,

    Using external RTC chip is not mandatory for TDA4. Basic requirement is to provide clock input on LFOSC pin. This can be provided through a crystal or RTC. EVM provides both the options as reference design but RTC clock input is disabled by default.

    If you want to avoid using both RTC and crystal to feed LFOSC pin, PMIC can provide the clock through CLK32KOUT but it is not enabled by default.

    - Pratap.

  • 0 in reply to M V Pratap Reddy
    Prodigy 130 points

    Hi Pratap,

    I have few more questions from your answer here.

    1. From PMIC datasheet. There's GPIO3 or 4 (VRTC domain) and GPIO8 or 10 (VIO domain) could act as CLK32KOUT is that correct?

    2. Although your answer is that CLK32KOUT could output the 32KHz clock. But it's not used in TDA4VM's SOM right? (PMIC-A)

    3. If TDA4VM's SOM are not going to use 32K clock from PMIC-A's CLK32KOUT then why they connected a 32K crystal(Y6) for PMIC-A?

    4. What is the pin VBACKUP in PMIC's purpose? I just guess it should supply coin battery to support RTC function while the EVM connected to GND.

    Thank you.

    Jimmy.

  • 0 in reply to Jimmy Hsueh
    Prodigy 130 points

    Hi ,

    Is there anyone who can check with my questions above?

    Thanks.

    Jimmy Hsueh.

  • 0 in reply to Jimmy Hsueh
    TI__Intellectual 1170 points

    Hi Jimmy

    Sorry for delayed response. Please check below details.

    >> 1. From PMIC datasheet. There's GPIO3 or 4 (VRTC domain) and GPIO8 or 10 (VIO domain) could act as CLK32KOUT is that correct?

    Yes, that is correct. By default these pins acts as GPIOs

    >> 2. Although your answer is that CLK32KOUT could output the 32KHz clock. But it's not used in TDA4VM's SOM right? (PMIC-A)

    PMIC has ability to generate CLK32KOUT but this functionality is not available by default. You need to reconfigure the PMIC to enable CLK32KOUT, By default these pins act as GPIO.  

    >> 3. If TDA4VM's SOM are not going to use 32K clock from PMIC-A's CLK32KOUT then why they connected a 32K crystal(Y6) for PMIC-A?

    OSC32KIN input is used by PMIC for internal RTC operation. This is needed to enable the PMIC RTC functionality irrespective of we use CLK32KOUT or not

    >> 4. What is the pin VBACKUP in PMIC's purpose? I just guess it should supply coin battery to support RTC function while the EVM connected to GND.

    Yes, that is correct VBACKUP for providing backup battery power when main power is OFF. 

    - Pratap.