TCA9548A: TCA & PCA PassFET hangtime Effect

Matt Qi

Intellectual 2470 points

Part Number: TCA9548A

Hi team,

Could you please help check whether our TCA and PCA series products may have the same signal problems?

Which is called as "PassFET Hangtime" effect internally.

TCA9548A: TCA9548APWR Master Interface Signal Issue - Interface forum - Interface - TI E2E support forums

PCA9306: Slave interface signal quality issue - Interface forum - Interface - TI E2E support forums

And whether this effect can influence the SI problem?

My understanding:

The PassFET hangtime is much shorter than the signal period and may not influence the rising/falling edge. And once my customer use our products within the frequency bandwidth range. The PassFET hangtime effect will not influence at all.

Is my understanding right?

Best Regards,

Matt.

8 months ago

0 Clemens Ladisch 8 months ago

Guru 276740 points

All devices that use such a pass transistor (some level level shifters, all I²C switches/muxes) have this effect. Due to the low speed of I²C, this has no effect on signal integrity. (Note that typical I²C rising edges are much slower than that.)

0 Alex Vish 8 months ago

TI__Genius 10552 points

Hi Matt,

The resources you provided and your understanding is correct - that all I2C switches/muxes will have this PassFET hangtime effect. As mentioned, due to the extremely small timescale of this hangtime, it will not influence your signals.

Let me know if you have any other questions here.

Regards,

Alex