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Does pulling-up resistor value matter?

Anonymous
Anonymous


Hi All,

 

I would like to ask a question about pull-up resistor.

 

 

 

 

Regarding its value, for example, those for I2C_CLK and I2C_DATA, I have found that on Spectrum’s EVM6437 board, the pulling-up resistors for these two signals are 2.2K, whereas

1.      On another board they use 1.2K

2.      And some other people use 4.7K for OmniVision's SCCB interface (variant of I2C)

 

Does the value matter very much? I think as long as the signal is pulled up/down and the current is not too big, either of the above should work. Is it true?

 

 

 

Zheng

  • 0
    TI__Genius 16810 points

    We used 2.2K on most of the TVP5xxx EVMs. You are correct, all of these values should be OK.   Larger resistors will result in slower SDA/SCL signal rise times, depending on I2C bus loading and the number of devices on the bus.

  • Anonymous
    0 Anonymous in reply to Larry Taylor

    Dear Larry,

     

    I see it, thanks very much.

     

     

    Zheng

  • Anonymous
    0 Anonymous in reply to Anonymous

    Dear Larry,

    Have you ever tried to use I2C controller of DM643x chips to communicate with ICCB interface of OV? I only know OV created SCCB in order to evade the license fee from Philips, and they are very similar, but how large is the difference? Can it work with I2C controller or not?

     

    Zheng