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issue with the TXS02612

Kamal Najmi
Expert 3435 points
Other Parts Discussed in Thread: TXS02612

I am having issues with the TXS02612 and a SD Card. The setup is the following:

 

We developed a CPU module with Freescale CPU, TXS02612 and a eMMC. The Module is placed in a Mainboard/Baseboard which has an SD-Card Holder. In addition to the TXS-Device we have Resistors to short the TXS-Device (if not placed). With the Resistors placed and the TXS not placed – the SD Card Interface works. The schematics are shown below the text.

 

I analyzed the CMD-signal with a High-Speed Scope with active probes – the problem is, that at some point the device starts ringing and the communication fails (because of the direction sensing, I guess). I also analyzed the parts behavior with a function generator – the critical load capacitance seems to be at around 60 pF, which I can’t imagine to have in my design. The routed signal length from the TXS to the card is 180 millimeters.

 

What can I do to make the interface work with the TXS?

Doc1.docx

  • 0
    TI__Intellectual 2530 points

    Hi Kamal

    This unfortunately looks like the one-shot oscillation. The "speed-up" circuitry you see in the block diagram are the one-shot accelerators.

    Driving that large lumped load capacitance directly depends on the one-shot duration (~10 to 30ns). The oscillations you see is the artifact of the architecture.

    Few suggestions:

    1)Please make sure the power up sequence is followed as advised on page 15 of the datasheet

    2) You can try to add a series resistor with an impedance same as the total impedance of the signal path. You still have to keep in mind to meet the VIL, VIH levels.

    3) SN74AVCA406A is a direction controlled part, if you have an option to use it. It is better as it can handle higher current and it might help

    Thanks

    Thanks