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LMK03328: I2C access and PDN

user4779049
Expert 2355 points
Part Number: LMK03328


He Team,

Please advise me on a question bellow:

1. During the I2C access, PDN pin is set to Low, LMK03328 may pull SDA line to Low.
2. Once it happens, LMK03328 is keeping SDA low even though PDN returns to High.
3. The problem occurs when I2C access, other than LMK03328 on the same bus, is taken place.


I2C Access -----------XXXXXXXXXXX-------------------

　　　　　___________
SDA 　　　　　　　　　XXX____________________
　　　　_________________ 　　　　　____________
PDN 　　　　　　　　　　　|________|

Q1. Is this expected behavior?

Q2. If so, are there any way to recover from this situation?

Q3. Is there any workaround to be free from this trouble?
Is it the only solution that keeping PDN high during I2C access?

Q4. LMK03328 Datasheet recommends to toggle PDN to low for short
period time, after power up, do you need to hold I2C access during
this instance?

Mita

  • 0
    TI__Genius 9920 points
    Hi Mita,
    It would happen.
    LMK03328 datasheet had highlighted "The PDN pin of LMK03328 should be high before any I2C communication on the bus. The
    first I2C transaction after power cycling LMK03328 should be ignored."

    The PDN pin (active low) can be used both as device power-down pin and to initialize the device. When this pin
    is pulled low, the entire device is powered down. When it is pulled high, the power-on/reset (POR) sequence is
    triggered and causes all registers to be set to an initial state. The initial state is determined by the device control
    pins as described in the Device Configuration Control section. When PDN is pulled low, I2C is disabled. When
    PDN is pulled high, the device power-up sequence is initiated as described in Device Power Up Sequence and
    Device Power Up Timing.

    If LMK03328 work normally with power up, there is no necessary to toggle PDN. When LMK03328 is running normally, PDN should be hold in high.

    Regards,
    Shawn
  • 0 in reply to Shawn Han
    Expert 2355 points

    Shawn-san,

    Thank you for the answer.

    Mita

  • 0 in reply to user4779049
    Guru 19785 points

    Hi Shawn-san,

    I have additional question to this topic.

    I found following description in the datasheet.

    What do you mean by "The first I2C transaction after power cycling LMK03328 should be ignored" ?

    Does this mean that LMK03328 requires one dummy I2C access before start programming once after power up ?

    Would you elaborate on this statement ?

    Best Regards,

    Kawai

  • 0 in reply to Kawai
    TI__Genius 9920 points

    Hi Kawai,

    That's meaning the 1st I2C operation after power up could be not available. I2C circuits just enter initial state after the 1st I2C transaction.

    A good method is to read ID registers (R0-R4) from LMK033x8 firstly.

    The 1st I2C read operation could be ignored, from the 2nd I2C read operation, we should get correct ID values. (For example, read R0 twice )

    When we confirmed these ID numbers are OK, we could continue to write/change other registers by I2C.

    Regards,

    Shawn

  • 0 in reply to Shawn Han
    Guru 19785 points
    Hi Shawn-san,

    Thanks for your prompt reply.

    I believe user normally does not (or hesitate to ) read and confirm the registers in the initial register programming in their system. (Write only)
    If this is the case, I believe two dummy read commands would be good enough.

    What would be your recommendation ?

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Genius 9920 points
    Hi Kawai,
    It works.

    Regards,
    Shawn
  • 0 in reply to Shawn Han
    Guru 19785 points
    Thanks Shawn-san.

    I'll recommend this procedure.

    Best Regards,
    Kawai