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TCA9803: operating frequency will support 3MHz

Arumugam Palaniyandi
Expert 1040 points
Part Number: TCA9803

Hi,

In our design we have consider I2C buffer from TI part TCA9803. 

We understood from the datasheet the operating frequency is 400KHz. 

In our case we may need to run upto 3MHz for I2C bus. 

The TCA9803 will support up to 3MHz ?? If not support could you please suggest TI equivalent alternate buffer with higher speed .

Thanks and Regards,

Arumugam.P

  • 0
    TI__Mastermind 48195 points

    Hi Arumugam,

    3MHz is very fast for an I2C bus. TCA9803 is only specified up to 400kHz but is quite capable of driving higher speeds such as I2C fast mode at 1MHz in certain systems. Increasing speeds further to 3MHz will further constrain the requirements of the rest of the system to allow for transition times and propagation delays to be short enough to support such short bit-times. 

    The main constraint here will be the load presented on the buffer's SDA/SCL lines. The more capacitance that is present here, the longer these delays will be. Looking at the specific example of propagation delay, the maximum specified on the device datasheet is 260ns. Because the bit-time at 3MHz is 333ns, this will not suffice as the signal will have to propagate both ways in a single bit for ACKs to be seen in time. However, as bus capacitance decreases, this delay will become closer to (or even less than) the typical specification (around 120ns).

    In short: it depends on the system whether or not TCA9803 will be able to support 3MHz. In an ideal situation where bus capacitance is low and other delay sources are minimal, the buffer will be able to support such speeds. However, in systems with long traces or a large number of I2C devices on the bus, the system load will lower the maximum achievable data rate. This trend will be true for any I2C buffer in a system. I would recommend testing this device in a setup that is similar to the end-system to simulate how the system load will affect the achievable data rate. 

    I hope this helps. Let me know if I can answer any other questions.

    Regards,
    Eric Schott