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SN74AVC16T245 data rate, OE tied to GND, power dissipation?

chip
Prodigy 55 points
Other Parts Discussed in Thread: SN74AVC16T245

Hi,

I am interested in using the SN74AVC16T245 to translate 1.8V data signals up to 3.3V.

The SN74AVC16T245 data sheet says 380 MBPS maximum data rate between 1.8V and 3.3V, and the maximum delay is 3.3 ns.  This part should then be OK for a 275 MSPS data rate, correct?   What is the maximum clock speed than could be used with the SN74AVC16T245, is it about 150 MHz?

Next I have a question about the OE pins, the data sheet says to use a pullup resistor and pull OE up to VCCA during power up and power down.   I would like to just keep the OE pins tied to GND and power up/down VCCA and VCCB.   Is it OK to do this or will it damage anything?  I'm not concerned about data integrity during power up or power down.  I did not want to use a separate circuit or control signal for the OE pins if I don't have to.

Finally, power dissipation in the voltage translator appears to be a function of the switching rate, if my application is pulsed (for example a duty cycle of 10%) and I stop switching the data inputs  the power dissipation should drop significantly, correct?

Thanks,

Chip

  • 0
    TI__Expert 6335 points
    chip,

    Please allow me a few days to get back to you with the answers. Thanks.

    Best Regards,
    Nirav
  • 0 in reply to Nirav Patel
    Prodigy 55 points

    Hi, It's been a week, could you please check on this?

    Thanks.

    Chip

  • 0
    TI__Expert 6335 points

    Chip - Sorry for the delayed response. My feedback is below:

    chip said:

    The SN74AVC16T245 data sheet says 380 MBPS maximum data rate between 1.8V and 3.3V, and the maximum delay is 3.3 ns.  This part should then be OK for a 275 MSPS data rate, correct?

    Not necessarily. I beleive that MSPS (Mega Symbols Per Second) does not always equal MBPS (Mega Bits Per Second). The actual data rate is dependent upon the number of bits that are encoded/carried by a symbol.

    Generally speaking: Bits Per Second = (Symbols Per Second)*(Number of Bits/Symbol). For the SN74AVC16T245, it would support 1 bit/symbol at 275 MSPS with VCCA = 1.8V and VCCB = 3.3V

    chip said:

    What is the maximum clock speed than could be used with the SN74AVC16T245, is it about 150 MHz?

    Maximum Clock Frequency = (Maximum Data Rate)/2 --> 190 MHz for 380 Mbps transmission.

    chip said:

    Next I have a question about the OE pins, the data sheet says to use a pullup resistor and pull OE up to VCCA during power up and power down.   I would like to just keep the OE pins tied to GND and power up/down VCCA and VCCB.   Is it OK to do this or will it damage anything?  I'm not concerned about data integrity during power up or power down.  I did not want to use a separate circuit or control signal for the OE pins if I don't have to.

    Yes you may tie the OE pin to GND without damaging the SN74AVC16T245

    chip said:

    Finally, power dissipation in the voltage translator appears to be a function of the switching rate, if my application is pulsed (for example a duty cycle of 10%) and I stop switching the data inputs  the power dissipation should drop significantly, correct?

    Yes. A reduced switching rate would reduce power consumption. You can refer to this app note for more details.

    Best Regards,
    Nirav