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I2C comm error with PCA9518D

Edm
Prodigy 30 points
Other Parts Discussed in Thread: PCA9518

I have been using NXP's PCA9518D and I2C communication is fine. However, once i started switching to TI's PCA9518D, my I2C communication error starts going up in a 12hr test. Error ranges from lost communication to a module to no ack response.

My question is; Is the TI PCA9518D a direct replacement or substitute to NXP's PCA9518D? I looked over the datasheet and could not find any difference between them. I tried changing pullups when using the TI ic but it did not help.

I have changed the ic to NXP in 5 different boards now and they all provide zero error counts for i2c comm issue in an overnight test. Any help is appreciated.

Thanks

  • 0
    Guru 22270 points

    Hello Edmond,

    They should be identical as you have noticed from both spec sheets.  I would suggest adding 100 nF decoupling cap from VCC to ground, directly on the chip to see if that helps.  The NXP could be more tolerant of noise.  The only time I have noticed problems with the I2C is if my wires to the device are too long.  One centimeter was the difference between errors and error free communication.

  • 0 in reply to Greenja
    Intellectual 600 points
    I have a lot of problems wit glitches on the clk line caused by the pca9518. Especially when a slave releases the clock. This causes a lot of errors.
    Could be a reflection problem of the bus, maybe that is the reason thta the 100Ohms resistors mentioned elsewhere in the forum work.
    Increasing bus capacity improves behaviour, however exchanging the Texas part for a NXP pca9518 eliminates the problem.