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SN74CBTD3384DW and HPI on DSP TMS3206713

Michael Jones52345
Prodigy 60 points
Other Parts Discussed in Thread: SN74CBTD3384

Hello,

I would like some recommendations for interfacing to the HPI on dsk6713.

I am using a 5V micro controller as host that drive pins at 10mA.

I am currently trying out the following bus switch/voltage translator. 

SN74CBTD3384DW

Would a line driver/buffer be more appropriate? 

Anybody have any suggestions.

Thanks

FNG

  • 0
    TI__Mastermind 46480 points

    The CBTD device is probably not the best choice if you ar running at any kind of speed.

    We have other switches that can translate and run faster but none of them will have drive.  The drive will come from the device on the input side since they are switches.

    If you need a part with drive we have duel voltage level translators that can do this. LVC8T245  8 bit or LVC16t245 16 bit 

    SN74LVC8T245     SN74LVC16T245

    If you do not need to go both directions you can us any CMOS part that is over voltage tolerant on the inputs.

    for instance the LV244 LVC245  They will translate down to Vcc.

  • 0 in reply to Chris Cockrill
    Prodigy 30 points

    We are translating a +5V PCI bus to a +3V3 PCI bus using the SN74CBTD3384. This is an inherited circuit.

    However, this does not perform satisfactorily. Even with the VCC for the device set to 4V5, the output is higher than allowed for our +3V3 device.

    Using VCC set to 4V0 gives satisfactory results, but is outside the specified VCC range for the switch.

    Your previous comments state:

    "We have other switches that can translate and run faster but none of them will have drive.  The drive will come from the device on the input side since they are switches."

    Which switches do you mean?

    Do you have any comments regarding the SN74CBTD3384? I feel it is very poorly specified and does not perform according to the VCC versus Vout graphs in the datasheet.

    Do you have any data regarding operation of the SN74CBTD3384 at 4V0? Could this be guaranteed?

    Thanks

    Brian C

  • 0 in reply to Brian Carter
    TI__Mastermind 46480 points

    Thes part are for very low frequency.  If you are running faster than 1Mhz you should use either

     SN74CB3T3384 wich would require 3.3V Vcc

    or

    SN74CBT3384A - SN74CBT3384C  with an external diode in series with Vcc. This would be the same type part as CBTD but would not charge pump when you get to higher frequencies

    CBT + diode.docx