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TPS53681: Tps53681 related issues

user4838693
Prodigy 190 points
Part Number: TPS53681

HI,

I have some questions about tps53681. Can you help me have a look? As follows:

1.What is the default configuration of the chip sent out by the factory? I now have two batches of chips.

One batch has output. The value of the register of 0x02 is 0x17, and the output voltage is 0.8V and 0.9V respectively.

The other batch of chips has no output, and the value of the register of 0x02 is 0x1b

Two batches of chips, register configuration is not the same, so I want to ask the chip factory default configuration is what?

2.What is the PEC of tps53681? Can PEC be closed? If I can shut it down, what should I do?

  • 0
    TI__Genius 11095 points

    Hello, 

    1- There was a change to the NVM defaults on this device in Jan 2019. The updated NVM defaults correspond to the values currently in the datasheet on ti.com now. A PCN notification was sent to all device customers at the time, but it may be possible to get some of the older material if you ordered through a distributor, or before the old material was depleted (this was a running change). 

    2- PEC is an optional feature. Simply do not sent clock pulses for the PEC byte to not use it. The device will only check the PEC for validity if one exists. 

  • 0 in reply to Matt Schurmann
    Prodigy 190 points

    Another  question :

    Is the PEC byte of all chips the same for tps53681?

  • 0 in reply to user4838693
    TI__Genius 11095 points

    Hello, 

    Are you referring to the NVM CRC, or the PEC function? 

    The NVM CRC is the same for every device shipping from TI. Note it did change when we introduced the NVM change I listed above. 

    PEC bytes are calculated based on the bytes in a transaction. The calculation is the same formula every time, but each transaction will have different data bytes (including the address of the device itself), and cause the correct PEC value to be different. 

  • 0 in reply to Matt Schurmann
    Prodigy 190 points

    Hi,

    I need to save some parameters to NVM.So I want to know the value of PEC bytes

    So, as you said, if the device address is fixed and the operation registers are the same, such as 11h, then the value of PEC byte of each device should be the same, right?

  • 0 in reply to user4838693
    TI__Genius 11095 points

    If all of the inputs are the same (e.g. device address, register address, data value) every time, the PEC will be the same. Writing different data to different register addresses, or the same data to different device addresses will change the PEC byte. 

    It would more robust to implement the calculation in your software. But for something "quick and dirty" there is a convenient calculator online (not made by TI) to calculate different CRC calculations. For SMBus PEC you can use the standard CRC8 at this site. 

    Example:

    Device address = 54d . 

    Write PAGE (cmd address 0x00) = data 0xFF. 

    For writes... set the direction bit to 0b, and then the address byte is (54d<<1 + 0) = 0x6C

    So the transaction bytes used are for calculation are <Dev Addr + W><Reg Addr><Data Value> = 0x6C 0x00 0xFF. Using the site above to calculate CRC8 for these bytes, gives the PEC byte is 0xCC. 

    So, finally, the bytes sent to the device are 0x6C 0x00 0xFF 0xCC, where 0xCC is the PEC. 

    http://www.sunshine2k.de/coding/javascript/crc/crc_js.html