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Auto sensing Level Translators supports 1.2V to 5.5V I/O

Ahamed Faize
Intellectual 260 points
Other Parts Discussed in Thread: LSF0108

Hi,

We need 8 channel Level translator with Auto direction sensing feature for GPIOs (I/O supply : 1.2V to 5.5V).

Requirement:
1) In our design, A side will be in fixed 3.3V supply & B side has to be changed from 1.2V to 5.5V.
2) Signals will translate from A to B & B to A using auto direction sensing feature.
3) There should not be any condition such that VCCA<VCCB or VCCB<VCCA.

Please provide the IC that suffices the above requirements.

Thanks

Ahamed Faize

  • 0
    Guru 317150 points

    The only device that can support this is the LSF0108. Vref_A must be connected to the lowest possible supply voltage (1.2 V), the resistor at Vref_B to a higher voltage; the voltages at the I/O pins and their pull-up resistors are independent from the reference voltages.

  • 0 in reply to Clemens Ladisch
    Intellectual 260 points

    Thanks for the quick response.

    In  LSF0108, always VrefA voltage has to be lower than VrefB for proper operation. 

    But in our our case. the conditions like VrefA>VrefB or VrefB>VrefA should not be there so that we can translate from 3.3V level on A side to any other levels(less than or greater than 3.3V) on Bside.

    So this part will not suffice the design considerations.

    Thanks

    Ahamed Faize

  • 0 in reply to Ahamed Faize
    Guru 317150 points

    As I said, Vref_A/Vref_B are independent from the signal voltages.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 45915 points

    Hey Ahamed,

    This will be the only device that can work here. I recommend watching these training videos on the LSF family to better understand what Clemens means here.

  • 0 in reply to Dylan Hubbard
    Intellectual 260 points

    Thanks. I will see the video.

    Just please confirm the below understanding :

    1) In A side the I/O line voltage can go maximum up to Vref_A & in B side the I/O line voltage can go maximum up to Vref_B.

    2) If the above is true, I/O line voltage on A side has to be lower than B side

    Regards,

    Ahamed Faize

  • 0 in reply to Ahamed Faize
    Guru 317150 points

    On the A side, the I/O line voltage can be higher than Vref_A.
    On the B side, the I/O line voltage can be lower or higher than Vref_B.

    The only restrictions are that Vref_A < Vref_B, and that no voltage is lower than Vref_A.

  • 0 in reply to Clemens Ladisch
    Intellectual 260 points

    Hi team,

    After going through the datasheet. I concluded the below major points.

    1) We can use this translator for translating multi voltage level(1.2V to 5.5V) at A side to multi voltage level(1.2V to 5.5V) at B side or vice versa.

    2) But for Using this translator for GPIO application as push pull configuration

                      - We have to fix the direction A to B or B to A. 

                      - For A to B translation, Pull up resistor has to be put on B side. For B to A translation, Pull up resistor is not needed. (Refer Figure 8 in LSF0108 datasheet)

                      - So It will not support Bidirectional communication for GPIOs.

    Please confirm the above. If it is true, we can't use this translator. Because we need the translator with push pull configuration, Auto-Direction Sensing, multi level voltage translation (1.2V to 5.5V at any side).

    Kindly provide your suggestion.

    Thanks,

    Ahamed Faize

  • 0 in reply to Ahamed Faize
    Guru 317150 points

    The LSF passes low voltages, and relies on the pull-up resistors to generate high voltages. This indeed means that all LSF outputs are open-drain outputs.

    In general, the LSF does support bidirectional communication with GPIOs. Why are open-drain signals a problem in your case?