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LSF0102: same function as LSF0102 but Enable refers to VREF_A

user4979899
Expert 3080 points
Part Number: LSF0102
Other Parts Discussed in Thread: TXS0102, LSF0204, TXS0104E-Q1, TXS0102-Q1

Hi Sir,

I'm looking for a same function as LSF0102 but Enable refers to VREF_A,

Could you please help to suggest any solution which have the 2 bits and enable pins refers to VREF_A level shifter solution?

Thanks

  • 0
    Guru 297970 points

    On the LSF devices, the EN pin is not a digital input and cannot use a lower voltage (see section 1 of Voltage-Level Translation With the LSF Family (SLVA675)).

    It might be possible to use the TXS0102 in your circuit.

  • 0 in reply to Clemens Ladisch
    TI__Expert 3080 points

    Hi Clemens,

    Thanks for your information sharing.
    TXS0102 is non-automotive and OP temp. max 85℃ is not enough for us.

    One more question, our customer think LSF0204 level shifter only use a biases MOSFET for level shifting, they need a pull up resistor somewhere to reach a defined state.
    (might also be internal pull up inside SoC or microcontrollers, where possible, but they might be too weak)
     

    But the interface of UART is Push-Pull, does LSF0204 need a pull-up resistor for these traces?
    And please also review our design of LSF0204, thank you.

  • 0 in reply to Clemens Ladisch
    TI__Expert 3080 points

    Hi Clemens,

    Thanks for your information sharing.
    TXS0102 is non-automotive and OP temp. max 85℃ is not enough for us.

    One more question, our customer think LSF0204 level shifter only use a biases MOSFET for level shifting, they need a pull up resistor somewhere to reach a defined state.
    (might also be internal pull up inside SoC or microcontrollers, where possible, but they might be too weak)
     

    But the interface of UART is Push-Pull, does LSF0204 need a pull-up resistor for these traces?
    And please also review our design of LSF0204, thank you.

  • 0 in reply to user4979899
    Guru 297970 points

    All I/O pins of the LSF0204 (that are actually used) require a pull-up resistor.

    It would be easier to use the TXS0102-Q1 and TXS0104E-Q1, which have integrated pull-up resistors.

  • 0 in reply to Clemens Ladisch
    TI__Expert 3080 points

    Hi Clemens,

    LSF0204 support push-pull and open drain. So external pull-up resistor should be depended on application.

    For UART, is it necessary?

    UART data rate is around 5MHz, FYI 

     

  • 0 in reply to user4979899
    TI__Guru 59750 points

    Hi Anne,

    The reason LSF is suitable for open drain or push pull applications is because of the external resistors and the flexibility to choose them.

    For push pull applications, the driver side is capable of driving a logic high and logic low. Hence, there is no need for placing external pullup resistors on the input side of LSF.

    For open drain applications like I2C, the driver side is capable of driving logic low but not logic high. Hence, an external pullup resistor is required for valid logic high level.

    In either case, an external pullup resistors will be required at the output side of LSF for enabling voltage level translation.

  • 0 in reply to ShreyasRao
    Prodigy 10 points

    Hi Shreyas,

    an external pullup resistors will be required at the output side of LSF for enabling voltage level translation.

    LSF0204 is the bidirectional translation, if using for push-pull signals, like UART

    TXD is from LSF A1(signal input) to B1(signal output) and RXD is from B2(signal input) to A2(signal output) , we need to place a pullup resistor on B1 side and A2 side, am I right?

  • 0 in reply to Ryan Su
    TI__Guru 59750 points

    Ryan,

    You are right about the resistor placements.