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SN74AXC8T245: Mbps when translating 1.2V to 3.3V

Iain Davis1
Prodigy 245 points
Part Number: SN74AXC8T245

Hello,

I tried to ask a related question to this thread (yet didn't work): RE: SN74AVC16T245-Q1: Question about Maximum Data Rates

Very interested in understanding what the data rate would be when translating from 1.2V to 3.3V.

The 'AVC' part in the thread referenced above lists 100Mbps as a maximum when translating to 1.2V - would it be the same/similar for the 'AXC' family?

What data sheet parameters are used to determine the maximum data rate?

Thank you in advance,

Iain

  • 0
    Guru 243080 points

    For the 1.8 V to 3.3 V case, the datasheet says "up to 380 Mbps", which corresponds to 2.6 ns per bit. The worst-case propagation delay for a 1.8 V source is 5 ns, so the actual translation takes at most 2.6 ns, and the remaining 2.4 ns are used up for switching the output. So for a 1.2 V source, where the specified propagation delay is 8 ns, and assuming that the output at the same voltage has the same switching time, we get 185 Mbps.

    I'm not sure if this estimation is entirely reasonable …

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 42600 points

    Hey Iain,

    I'm not sure of the validity of that method, but its result does agree with my answer which is that the AXC device will definitely meet the same data rates as the AVC device and would say it could reach upwards of 200 mbps. There's not really anything in the data sheet that can help determine the max data rate other than the output driver parameters. Typically, the limitation of the output driver and the size of the load will set the maximum operating frequency since you will need certain rise/fall times to provide good signal integrity. This FAQ should help with this estimation, but I would also recommend grabbing an EVM and adding the expected load to best illustrate the capabilities of the AXC device in your system. 

  • 0 in reply to Clemens Ladisch
    Prodigy 245 points

    Clemens,

    Thank you for the estimation (and walking me through it) - Much appreciated!

    Iain

  • 0 in reply to Dylan Hubbard
    Prodigy 245 points

    Hello Dylan,

    Thank you for your insight & reasoning... this also is greatly helpful (and appreciated).

    Iain