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XEVMK2EX: use of I2C level translator

Tarang Jindal68
Intellectual 820 points

Part Number: XEVMK2EX

Hello, 

In K2E EVM, Two type of level translators are used - PCA9306 and TCA9517

TCA9517 - this is used for I2C level translator and

PCA9306  - This is used for SMBus level translator. 

As per TCA9517  datasheet, this device can also support SMBus level translation. so, why EVM used two different parts. 

In our design, we need I2C-1 conncted to UCD9090 SMBus interface, so is it nessasary to use PCA9306  device or we can use TCA9517  device for the purpose? Please also mention the reason. 

Thanks and Regards

Tarang Jindal

  • 0
    TI__Guru**** 161600 points
    Hi,

    If you have a look at the board TRM:
    www.einfochips.com/.../EVMK2E_Technical_Reference_Manual.pdf

    Figure 1.1: Block Diagram of EVMK2E, you can see that PCA9306 level shifter is used on the PMBus (which is a variant of SMBus). And if you have a look at the data sheets of both devices (TCA9517 & PCA9306) you can notice that in the PCA9306 datasheet it is explicitly mentioned as PMBus compatible level translator, I guess this is the reason why the two devices are used in the design...

    In your case for UCD9090 interface, which is described as: "The UCD9090 is a 10-rail PMBus/I2C addressable power-supply sequencer and monitor.". Although PMBUS is a variant of the SMBUS (with small differences) and you'll probably be fine with both TCA9517 & PCA9306, I think it is better to use the PCA9306 level shifter.

    I am also adding the hw team to elaborate further if needed.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    TI__Mastermind 46460 points

    Tarang,

    The PCA9306 and the TCA9517 devices both support bridges from one I2C bus to another, including supporting different voltages.  However, their implementation is different.  The PCA9306 is a floating gate FET implementation that does not contain active output buffers.  The TCA9517 does contain output buffers.  Also, the TCA95xx devices have special considerations when cascading I2C buses.  That is why they are used on the EVM since cascading is in the design.  Either device can be used for simply bridging I2C buses.  You need to review the datasheets clearly if you are cascading I2C buses.

    Tom