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Linux/TPS65218: How do i get the rtc power on tps65218 chip through AM4378 driver.

WooSeok Nam
Intellectual 460 points
Part Number: TPS65218
Other Parts Discussed in Thread: AM4378,

Tool/software: Linux

Hi all.

I built a board based on the AM4378 EVM board.
And the PMIC chip uses TPS65218.

To maintain the RTC of the AM4378, I attached a coin cell to the TPS65218.
However, the TPS65218 did not supply 1.8v power.

What should I do?


Do I have to write something through i2c?
However, the 0x24 address is UU (used).

Which driver is the TPS65218 driver?

if there is a driver, what should I do ??

Please, help me......

I want the AM4378's RTC to be maintained through the cell coin battery and the TPS65218 even when the main power of the AM4378 is turned off.

  • 0
    TI__Genius 17380 points

    Hi WooSeok,

    I have assigned this part to the expert.

    (Please disregard initial post, I was mistaken)

  • 0
    TI__Expert 4155 points
    WooSeok,

    It appears you do have the battery connected correctly. There also shouldn't be any I2C writes that you need to make to get the device to run off of the coin cell. I would check the following first.

    1. Voltage on CC pin, just to make sure the coin cell is supplying the minimum of 2.2V
    2. PWR_EN pin when you disconnect power. I am not sure how the AM4378 reacts when it's other rails are turned off, but it could be shutting down the PMIC using this pin.
    3. PGOOD_BU pin. Should be high if DCDC5 and DCDC6 are in regulation.
    4. IN_nCC pin. Should be low if the device is running off of the coin cell.

    Thank you,
    Nick
  • 0 in reply to Nick Jakse49
    Intellectual 460 points
    Thanks for your reply.
    Checked them..
  • 0 in reply to WooSeok Nam
    TI__Expert 4155 points
    WooSeok,

    Would you be able to send me a register dump from the PMIC? I can try recreating this with your config and see if I get the same issue.

    If those pins are all behaving as expected, then I don't suspect any sort of issue with the physical board, unless the 1.8V rail was disconnected somewhere, in which case it wouldn't matter whether main power was on or off.

    A schematic of the processor side of the design might help too, but assuming those ports are just connecting straight to the correct AM4378 inputs I doubt there is a problem there.

    Thanks,
    Nick
  • 0 in reply to Nick Jakse49
    Intellectual 460 points

    Thanks for your reply.
    What does PMIC register dump mean?
    And how can i get the PMIC register dump?

    TPS65218 i2c address is 0x24

    That is busy..

  • 0 in reply to WooSeok Nam
    TI__Expert 4155 points

    WooSeok,

    By register dump I just mean the contents of all of the registers. I am not sure how you are communicating with the PMIC, but if you can read all of the register contents then I can go through it and see if there is anything that stands out to me, or see if I can replicate the issue.

    Section 5.3.1.18 in the datasheet goes into detail on how to read registers through I2C communication.

    Thanks,
    Nick

  • 0 in reply to Nick Jakse49
    TI__Expert 4155 points
    WooSeok,

    If you are still working on this issue I believe I may have found out why.

    Check the fseal bit in the STATUS register (bit 7, Register address 0x5).

    If it is 0 then try writing this sequence to the PASSWORD register (register address 0x10): 0xB1, 0xFE, 0xA3

    You may have to write it up to 3 times, but then the fseal bit should stay as a 1.

    Thanks,
    Nick