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LSF0108: LSF0108

Rohini E
Prodigy 80 points
Part Number: LSF0108
Other Parts Discussed in Thread: TXV0108, TXB0304

Tool/software:

Hi Team,

We are using LSF0108 in one of our designs to level translate signals between FPGA IO(1.2V) and USB3320

The max signal frequency is 60MHz and the data are bi-directional.

We have connected 2.5V to VREFB to maintain the BIAS Voltage

Could you let us know below circuitry is ok for the scenario mentioned

Thanks,

Rohini

  • 0
    Guru 316350 points

    This might work. But I do not know if the pull-up resistors are sized correctly. Both the other devices must be able to sink the total current through both resistors, and the low-pass filter formed by the pull-up resistors and the trace/device capcitances must not filter out your 60 MHz signals. I do not know these parameters.

    A buffered, direction-controlled translator like the TXV0108 might be a better idea; ULPI has the DIR signal for this.

  • 0 in reply to Clemens Ladisch
    Prodigy 80 points

    Hi Clemens,

    Thank you for the reply

    1. I have updated the Pullup values for

    Data frequency of 60MHz

    IOL of MAX10 is 10mA 

    IOL of USB3320 is 8mA

    Pin Capacitance @1.8V device is 4pF

    Pin capacitance @1.2V device is 10pF

    As per calculated below calculation we are using 475E(1% Tolerance) Pullup on 1.2V side and 576E(1% Tolerance) pullup on 1.8V side. Please confirm the tuned pullup values are good to go

    USB  Va 1.2       MAX10
    Ra 475  
    Ca 2.3  
    DATARATE 152.5553013 MBps
           
    Vb 1.8   USB3320
    Rb 576  
    Cb 4      
    DATARATE 72.33796296 MBps 5.651315789 Iol

    2. LSF0108 bias voltage is 0.8V and we are translating signals from 1.8V to 1.2V and vise versa

       To maintain the Bias voltage, we have connected 2.5V to VrefB but pullups(576E) on I/Os are connected to 1.8V. Hope this is fine

    Awaiting for your reply

    Thanks,

    Rohini

  • 0 in reply to Rohini E
    Guru 316350 points

    The MAX10's drive strength at 1.2 V is only 2 mA, but your total pull-up current is more than 5 mA. And you have to include the capacitances of the traces and of the LSF.

    As far as I can see, ULPI has pull-down resistors on the data lines, so you must not use a translator that requires pull-ups.

  • 0 in reply to Clemens Ladisch
    Prodigy 80 points

    Hi Clements,

    Will TXB0304 for our application

    Main consideration is 1.2V to 1.8V Bidirectional Translation and 60MHz data flow support

    Thanks & regards,

    Rohini

  • 0 in reply to Rohini E
    Guru 316350 points

    No; the TXB does not work with pull-up/-down resistors, and it does not support more than 50 MHz at these voltages.

  • 0 in reply to Clemens Ladisch
    Prodigy 80 points

    Do you have any suggestion for our application

    Main consideration is 1.2V to 1.8V Bidirectional Translation and 60MHz data flow support

    Thanks & regards,

    Rohini

  • 0 in reply to Rohini E
    Guru 316350 points

    TXV0108.

    Consider redesigning your system to use 1.8 V I/Os on the FPGA.