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SN74LVC8T245: maximum data rate for the part

Ramakrishna Bachimanchi
Intellectual 300 points
Part Number: SN74LVC8T245
Other Parts Discussed in Thread: ADS8353, SN74AXC8T245

Hello,

I am trying to use 74LVC8T245 to interface between fpga and ADS8353 and the logic translation is between 1.8 V and 5 V. I was looking for maximum data rate for this configuration and I couldn't find the information in the data sheet(may be I overlooked at something). Both clock and data signals go through the translator and the maximum clock is 50 MHz. I just want to make sure this is okay(I am sure it is, double checking) before starting the layout. I saw the same part on nexperia and the translation to 1.8V (75 Mbps) and I suppose this is every bit not the whole chip.I also saw the one bit and dual bit translators(74LVC1T45, 74LVC2T45) which have 75 Mbps when translating to 1.8V. It should be the same for 8T245 for each bit? Can someone please let me know the maximum data rate for this chip

Thanks,

Rama

  • 0
    Guru 316690 points

    The switching characteristics tables shows the maximum propagation delay; you can use this as an exxagerated worst-case estimate of the length of a bit:

    1 bit / 21.4 ns = 46.7 Mbps = 23.4 MHz

    The actual maximum frequency will be higher because the input voltage can change while the output is still switching. 75 Mbps (= 37.5 MHz) sounds around right.

    Is it really necessary for the digital interface of the ADS8353 to run at 5 V? At 3.3 V, you would be able to use the faster SN74AXC8T245 (or some other translator in the AXC family), or 1.8 V would not require translation at all.