PCA9548A: abnormal wavefom

Hailiang Zhang

Part Number: PCA9548A
Other Parts Discussed in Thread: TCA9548A

Hi Team，

The customer feedback that the falling edge of the I2C waveform is abnormal, please refer to the picture. may I ask if this is normal?

Thanks，

Regards,
Hailiang

over 2 years ago

0 BOBBY over 2 years ago

TI__Guru* 77381 points

Hi Hailiang,

This waveform should be fine.

This is an artifact of using pass FETs (the NFETs inside the TCA9548A used to level shift). Those hang times are generally below 50ns (I2C devices are all required to have 50 ns deglitch filters to remove this kind of concern). We've never seen an issue reported by a customer due to this hang time.

-Bobby

0 Hailiang Zhang over 2 years ago in reply to BOBBY

TI__Genius 11860 points

Hi Bobby,

I wonder if it is the same for TCAxx? Thanks.

Regards,
Haiilang

0 BOBBY over 2 years ago in reply to Hailiang Zhang

TI__Guru* 77381 points

I'm not sure what you mean by TCAxx, we have several TCA devices in the family. All devices that use a pass FET architecture for level shifting will run into this problem.

-Bobby

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PCA9548A: abnormal wavefom