Severe PCA9507 problem !!!!

[ilanr]

Title: Phantom clocks

Severe PCA9507 problem !!!! - #Phantom clocks

We have received a new batch of produced cards with PCA9507 assembled and observed that sometimes Phantom clocks are generated by the device on the A side (blue) (master connected on the B side(red) !

please see attached picture .

This did not happen in the previous batch of cards. No BOM changes were applied.

Did anyone ever encounter such a problem /

Any hints/directions to follow?

[guoweisun]

Hi,

Please attach your picture again!

[ilanr]

Please find picture attached

Also the main part of the electronic scheme

Thank you

[guoweisun]

You schematic is unclear and from your test waveform the  channel3/4 are 20.0v/div,something is wrong?

[ilanr]

Probe was 1:10 but not updated in scope cfg. So it was actually 2V

Please see a better picture of the design.

[guoweisun]

What are the B side of U1/6 connection? Do they connect with signal source?

[ilanr]

B side of U1 are pins 6 and 7

They are connected to the signal source (bus master)

U6 B side is also connected in parallel to the bus master, however, the Enable signals ensure that only one buffer is active

[guoweisun]

Hi

I note your U1/6  A sides have different of series resistors value and different pull up resistors value.

Do you change cross the issue product and good product with their PCA9507 to check the fucntion?

[ilanr]

Each side A is connected to a different bus segment with different devices. The terminations and PU are best fitted to the devices on the specific bus segment