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TCA9406: Rise/Fall time

Yuta Nishie
Genius 4925 points
Part Number: TCA9406
Other Parts Discussed in Thread: TXS0102, PCA9306, TCA9803

Tool/software:

Hi,

I would like to use TCA9406 with I2C Fast Mode. I2C Rise/Fall time has a lower limit, and rapid changes are not allowed.

1. I am currently adjusting it with an external pull up resistor, but the waveform does not become gentle. Could you tell me how to make the waveform gentle with an external component?

2. Also, is it correct to understand that this IC supports I2C Fast Mode?

Best Regards,

Nishie

  • +1
    Guru 316380 points

    The TCA9406 is essentially identical with the TXS0102, which was designed for high-speed signals.

    In most cases, the TCA9406 will work with other devices. If you want to ensure that the rise times of the I²C specifications are met, use other translators like the PCA9306 or TCA9803.

  • 0
    TI__Mastermind 21700 points

    Hello Nishie,

    Our apps team is current out today celebrating Labor Day (US Holiday). Allows us two days to respond back. Thank you for your understanding.

    Regards,

    Josh 

  • 0 in reply to Clemens Ladisch
    Genius 4925 points

    Hi Clemens-san,

    If you suggested another IC, is it correct to understand that it is difficult to adjust the signal transition time using TCA9406 and external components?

    Best Regards,

    Nishie

  • 0 in reply to Joshua Salinas
    Genius 4925 points

    Hi Josh-san,

    I look forward to your reply after the holiday. I would appreciate it if you could confirm my questions 1 and 2.

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    Guru 316380 points

    It might be possible to adjust the transition times by adding a series resistor or even an LPF filter. You'd have to experiment on your actual board.

  • +1
    TI__Mastermind 46703 points

    Hi Nishie,

    Yuta Nishie said:
    1. I am currently adjusting it with an external pull up resistor, but the waveform does not become gentle. Could you tell me how to make the waveform gentle with an external component?

    The TCA9406 has built in one-shot accelerators and 10k PU resistors on both sides of the device. The equivalent PU resistance is 5kohm, adding any external PU resistance only makes this PU resistance value lower (stronger PU to VCC). 

    The one-shot accelerators trigger on a rising edge. Once a certain voltage threshold is met, the one-shot triggers which acts like a very strong PU to VCC. You won't be able to adjust the PU strength much by varying the external PU resistance. This is why CLemens has suggested trying a different device that is more passive such as PCA9306 which does not have internal 10k PU resistors, or one-shot accelerators. 

    Yuta Nishie said:
    2. Also, is it correct to understand that this IC supports I2C Fast Mode?

    The TCA9406 should support I2C fast mode. 

    Regards,

    Tyler