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LSF0108: LSF0108 slew rate too slow

user4979899
Expert 3080 points
Part Number: LSF0108

Hi Sir,

My customer found the LSF0108 slew rate is too slow as below diagram CH1(CLK).

And also insert the schematic, FYI

Could you please help to comments how could we fix it?

Thanks

  • 0
    Guru 294900 points

    The application report Voltage-Level Translation With the LSF Family (SLVA675) says:

    5.4 What is the frequency range of the LSF?

    The LSF family can translate up at 100 MHz and down at 200 MHz with reasonably good signal integrity. Signal integrity for translation depends on many factors, including line capacitance, output load, and pullup resistor sizes. Generally, smaller pullup resistors allow faster translation, but at the expense of power.

    Those 10 kΩ resistors are certainly too large. Depending on the frequency, you might also want to reduce the pull-ups on the B side.

  • 0 in reply to Clemens Ladisch
    TI__Expert 3080 points

    Thanks for reply.

    Would you guide us what Vgate meaning is please?

  • 0 in reply to user4979899
    Guru 294900 points
    It's the voltage at the EN pin.
  • 0
    TI__Guru 59460 points
    Hi Anne,

    As per the datasheet, the VrefB and EN are connected together using the 200k biasing resistors.
    Here, you have another input connected to the EN pin, and connected to the VrefB pin. Please confirm the connection.
    Also notice that the 2 resistors on the B side are unpopulated even though they are designated as the output. Please let me know if you have any other concerns.
  • 0 in reply to ShreyasRao
    TI__Expert 3080 points

    One more questions, the C load here mentioned in datasheet as below is C Max (A, B), right ?

  • 0 in reply to user4979899
    TI__Guru 59460 points

    Hi Anne,

    There is no max as such for this device as compared to TXB/TXS.

    The Cload is referencing to the output and with smaller loading, higher Rpullup can be used or theoretically can achieve higher speeds at the expense of power consumption.