• State Answer Suggested
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 35 subscribers
  • Views 449 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

PCA9535: interrupt initial value

PCA9535: Tpv measurement failed in 100KHz I2C speed

Ben Kuo
Expert 7560 points
Part Number: PCA9535

Dear Team,

We have measured Tpv which follow datasheet figure7-2/7-3 and note B(0.7 × VCC on SCL to 50% I/O (Pn) output).

But the result is out of datasheet spec, could you share your comments with us?

Regards,

Ben

  • 0
    Guru 316690 points

    Apparently, the write actually happens at the falling edge of the clock.

  • 0
    TI__Guru 72751 points

    Hi Ben,

    Something about the yellow waveform looks a bit strange to me. It seems like prior to the measurement the signal is transitioning from HIGH to LOW, then only 3 clocks it transitions from low to high. For our device, we require atleast 9 clock cycles to transition from low to high or high to low. I'm a bit skeptical this is the Pn pin.

    From my testing/validation of this parameter, I recall the output actually changes at around 30% of the of the SCL ACK pulse. So usually the tpv time is actually negative. 

    Can you redo your measurement with the SDA/SCL pins and double check CH1 is indeed connected to the p-port.

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 7560 points

    Hi Bobby,

    We have remove C_load and measure Tpv timing again as attached picture.

    Is this what you mentioned about Tpv negative? Is this normal waveform of Tpv?

    Regards,

    Ben

  • 0 in reply to Ben Kuo
    TI__Guru 72751 points

    Hi Ben,

    That's correct. Normally I would expect this measurement to come out negative where the P-port changes before SCL hits 70% on the ACK pulse.

    -Bobby

  • 0
    Prodigy 10 points

    Hi Bobby

    We had found your new PCN device measurement was out of SPEC. Please help to confirm whether this parts have any risk.

    SPEC 200ns and measurement is 218.760ns which is out of SPEC. Thank you.

  • 0 in reply to Allen Liu
    TI__Guru 72751 points

    Allen,

    How iare you loading SCL and the P-Port? 

    Your scopeshots also seem to show a low resolution capture. Are you able to increase the resolution on the scope?

    -Bobby