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PCA9546A I2C MUX Bus Problem Why?

Question asked by Bernt Damm on Jul 29, 2020
Latest reply on Aug 11, 2020 by Tomas Vaverka

Hi,

I designed this into a new product or ours.

 

I notice that the chip frequently results in an I2C bus stuck event that needs recovery.

 

This occurs when writing the control register for a MUX selection, followed immediately bu a read to confirm the correct selection.

 

The bus will sometimes become stuck in that SDA remains low forever or until bus recovery procedure.

The bus become stuck at around bit 8 or Ack of read data address. See attached wave capture.

 

This happens at a frequency of around 1 in 1000 or in my case about every 3 minutes.

 

Bus operation is 100kHz.

 

What can cause this problem?

 

The bus signals are clear and beautiful. Is there a minimum time specification between a write followed by read ?

I cannot see it in the datasheet.

 

Regards

Bernt

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