SN74AVC2T245: Input transition rise and fall time for UART application

Duong Nguyen

Part Number: SN74AVC2T245
Other Parts Discussed in Thread: TXU0202, SN74AUP1T34, TXB0102, SN74AXC2T245

Hi TI team,

I would like to use SN74AVC2T245 for UART translator (1.8V <=> 3.3V)

But i worry about the maximum Input transition rise and fall time.

UART speed is around 1Mhz and the transition rise/fall time is around 15ns/V

But the limit transition rise and fall time of SN74AVC2T245 is 5ns/V

Any risk when i use SN74AVC2T245 for UART application ?

+1 Clemens Ladisch over 2 years ago

Guru 243980 points

I'd recommend to use the TXU0202, when it is available. Alterntively, use 2x SN74AUP1T34 to translate up an down.

0 Duong Nguyen over 2 years ago in reply to Clemens Ladisch

Hi Clemens,

Thanks for your advice.

We have the issue when using TXB0102, so after that, TI engineer recommend use SN74AXC2T245 which has the transition rise/fall time is 10ns/V.

But I think 10ns/V still does not meet UART transition rise and fall time. Right?

What do you think if we still use SN74AVC2T245 or SN74AXC2T245?

Because our customer use SN74AVC2T245 in UART for a lot of projects and it looks working well

ANW, I will consider SN74AUP1T34 for our project.

Thanks,

+1 Clemens Ladisch over 2 years ago in reply to Duong Nguyen

Guru 243980 points

The linked FAQ describes what can happen. Cross currents and oscillations are not necessarily immediately noticeable.

+1 Dylan Hubbard over 2 years ago in reply to Clemens Ladisch

Hey Duong,

To add to what Clemens stated, this behavior can also vary in severity over PVT.

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