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DS100BR210 in SMBUS master mode connected to EEPROM

Reisswolf
Prodigy 80 points
Other Parts Discussed in Thread: DS100BR210, DS100KR800

Hello,

I'm designing a PCB with the DS100BR210 in SMBUS master mode connected to EEPROM. I'm a bit puzzled with the statement on page 17 "The external EEPROM device must support 1 MHz operation" because evaluation board schematic suggests a 24C08 EEPROM. The standard 24C08 seem to be working up to 400 kHz but I couldn't find any working up to a 1 MHz. Also the 24C08 is an I2C version and not SMBus compatible.

So is the 24C08 a good choice or can someone recommend a different EEPROM?

I'm also wondering if the DS100BR210 as well as the DS100KR800 would work as a I2C slave? I was hoping that someone tried that already. I would appreciate some comments on that.

Thanks in advance!!

 

  • 0
    TI__Mastermind 29655 points
    Hi Reisswolf,

    The reason the EEPROM needs to support 1 MHz operation is that in EEPROM Master Mode, the repeater nominally operates at 400 kHz, but it could potentially operate at up to 520 kHz, due to lot variance. The Atmel AT24C08C supports both 1 MHz and 400 kHz operation, so this should be a safe option. The repeater can function with I2C compatible EEPROM.

    Yes, the repeaters work as both I2C master and slave. If you choose to use EEPROM master mode, the repeater will take control of the SDA/SCL bus and load the appropriate parameters from EEPROM when READ_EN# is toggled low. When a load is successfully completed, the repeater will revert back to Slave Mode.

    Hope this helps, and please let me know if anything is confusing.

    Thanks,

    Michael
  • 0
    TI__Expert 3175 points
    Hi Reisswolf,
    When DS100BR210 is set up as SMBus master, it generates a SCL clock from its internal oscillator. It is nominal 400KHz, but will be as high as 500KHz in process variations. For EEPROM devices, they usually specify their speed grade as the maximum, for example, a EEPROM rate at 400KHz actually meant max 400KHz in their specifications. For this reason, we need to call for a EERPOM that supports >400KHz, and the next speed grade is 1MHz.
    I will ask my colleague to recommend a couple EEPROM devices that can support >400KHz.
    regards,TK Chin
  • 0 in reply to T.K. Chin
    Prodigy 80 points

    Thanks Michael and TK Chin for your answers!

    So, I do understand now where the requirement for 1 MHz comes from. My design also contains a DS100KR800 and I recently added the DS100BR210 to add two additional channels.

    I went back and checked the DS100KR800 datasheet. The requirements for the SMBUS master on page 12 is given as: "The external EEPROM device address byte must be 0xA0'h and capable of 400 kHz operation at 2.5V and 3.3V supply." The timing specifications indicate a max. of 520 kHz in master mode which is same as it is for the DS100BR210. So does that mean the DS100KR800 datasheet should also require 1 MHz instead of 400 KHz?

    The 1 MHz requirement applies only for the master mode of the DS100xxx, right? As a slave device it would work at slower clock speed also. Is that correct?

    Regarding my second question: There are some differences between SMBus and I2C. That's why I was wondering about the compatibility to I2C. I was hoping that I can use my regular I2C master, that I have in the system, to control the DS100xxx devices. Would that work?

    Thanks for your help!

  • 0 in reply to Reisswolf
    TI__Mastermind 43795 points

    Hi,

    When using the EEPROM configuration method with DS100BRxxx or DS100KRxxx devices a 1 MHz capable EEPROM is recommended.  The internal clock in the DS100 device can run in excess of 400 KHz. 

    There are several EEPROM devices which will work at this speed.  I have included the url of one here, www.atmel.com/.../atmel-8700-seeprom-at24c01c-02c-datasheet.pdf

    ‎I have not seen issues using I2C compliant masters with our slave interface.

     
     
     
     
     
     
    Regards, Lee
  • 0 in reply to Lee Sledjeski
    Prodigy 80 points

    Lee,

    Thank you very much for the clarification and the link you provided. I think this discussion saved me a lot of time I would have had to spend during testing. I appreciate everyones help! 

    Regards