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TPS65912: TPS659122, why LDO1 and LDO4 LIMIT register is read only?

Osama Bouz Al Asal
Prodigy 30 points
Part Number: TPS65912

Hello,

unfortunately i can not change the limit register values per I2C, but the data sheet says that the two registers are writable.

LDO1 is limited to 0.925V and LDO4 to 2V, is it possible to change these registers to different values?

Thanks,

Bouz Al Asal

  • 0
    TI__Genius 10885 points
    Hi Al Asal,

    These voltages appear to describe the TPS659121 (top two rows), instead of the TPS659122 (bottom two rows). Looping in the product expert to confirm.

    The descriptions for the MAX_SEL registers state "If MAX_SEL is set to any other value that 0x00 or 0x3F, the register is set to read only."

    Best Regards,
    Rick S.
  • 0 in reply to Richard Solarski
    Prodigy 30 points

    Hi Rick,

    thanks for the answer.

    The default values for the other registers are correct for TPS659122. "e.g., DCDC1_limit".

    Only the default values for the limit registers for LDO 1 and LDO 4 are wrong.

    Best Regards,
    Bouz Al Asal

  • 0
    TI__Mastermind 49361 points
    Hi, Bouz Al Asal,
    What's the exact part number you're using? Please refer to datasheet page 63 section "7.28.1 Register Format" which gives you clear picture about the register access.
    Please let's know if you have more questions.
  • 0 in reply to Phil Yi
    Prodigy 30 points

    Hi Phil,

    i use TPS659122YFFR.

    According to the data sheet, the LDO1_LIMIT and LDO4_LIMIT Register default values for TPS659122 must be 0x3F (RW).
    But the values are unfortunately different.
    The real default values are: (read via I2C)
    LDO1_LIMIT: 0x5
    LDO4_LIMIT: 0x28
    LDO1 is limited to 0.925V and LDO4 to 2V.


    Because the default values are not 0 or 0x3f, these registers are read only.


    Best Regards,
    Bouz Al Asal

    According to the data sheet, the LDO1_LIMIT and LDO4_LIMIT Register default values for TPS659122 must be 0x3F (RW).
    But the values are unfortunately different
    The real default values are: (read via I2C)
    LDO1_LIMIT: 0x5
    LDO4_LIMIT: 0x28
    LDO1 is limited to 0.925V and LDO4 to 2V.
     
    we need 2.5 at the LDO and 3.3V at the LDO 4
     
    because the default values are not 0 or 0x3f, these registers are read only.
  • 0 in reply to Osama Bouz Al Asal
    TI__Mastermind 49361 points
    Hi, Bouz Al Asal,
    It looks like the device you're using has been changed from its default setting. If you do need 2.5V at the LDO1 and 3.3V at the LDO4, you may buy brand new device with its default setting and change it once from its default settings.