TXS0102: Regarding I2C waveform countermeasures

Shinji Kato

Prodigy 60 points

Part Number: TXS0102
Other Parts Discussed in Thread: PCA9306, LSF0102

Connecting CPU (PIC) and TXS0102.

I have the following waveform, is there any solution?

4 months ago

0 Clemens Ladisch 4 months ago

Guru 261460 points

The TXS has edge accelerators to allow high data rates. Apparently, your bus capacitance is so high that the accelerator cannot (dis)charge it completely.

Where did you measure these spikes? Are they visible only at the TXS pins, or also at the I²C devices?

I²C is a slow protocol and does not need edge accelerators. You could use a simpler translator like the LSF0102/PCA9306.

0 Jack Guan 4 months ago

TI__Mastermind 20941 points

Hey Shinji,

Similar to what Clemens' mentioned, this is a side effect of using the TXS0102 to drive signals across long cabling/ PCB traces. The TXS0102 uses one shot circuitry to speed up the rise times, but if the output capacitive load is too high, the one shot can time out prematurely as we see here.

You may also see Leveraging Edge Rate Accelerators with Auto-Sensing Level Shifters for further clarification.

Regards,

Jack

0 Shinji Kato 4 months ago in reply to Clemens Ladisch

Prodigy 60 points

Thank you for answering.

Also slightly observed on I²C devices.

Please tell me the difference between LSF0102/PCA9306 that you introduced.

Which one is suitable?

+1 Clemens Ladisch 4 months ago in reply to Shinji Kato

Guru 261460 points

There is no practical difference between the LSF0102 and PCA9306.

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TXS0102: Regarding I2C waveform countermeasures