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Original question:

SN74LVC2G17: Output stays high

SN74LVC2G17: DESIGN QUERY

Sreejitha VM
Prodigy 170 points
Part Number: SN74LVC2G17
Other Parts Discussed in Thread: TXU0102, SN74LV1T34, SN74LVC2G07, SN74LV6T17

We are using SN74LVC2G17 for up conversion in our design.

We have given VIN as 3.3 V and VCC as 5V. But it was not giving the output voltage. Is this IC is specifically for down conversion only ?

  • 0
    Guru 282290 points

    At 5 V, VT+ is 3.4 V. So 3.3 V signals are not guaranteed to work.

    For up-conversion, you need a buffer with lowered input thresholds like the SN74LV1T34, or an actual level shifter like the TXU0102.

  • 0 in reply to Clemens Ladisch
    Prodigy 170 points

    ok, so that means if I am giving 3.4V input and vcc as 5V to SN74LVC2G17, it will give output as 3.4V only, will not do up conversion.. Please correct me if I am wrong.

    And also please suggest a dual channel up conversion IC.

  • 0 in reply to Sreejitha VM
    Guru 282290 points

    No, a digital output always is either low (0 V) or high (5 V).

    The problem is that the input might not be read correctly, i.e., it might still be low at 3.3 V.

  • 0
    TI__Intellectual 1100 points

    Hi Sreejith,

    I agree with what Clemens has said. Your current solution will not work reliably because the 3.3V inputs signal will not be able to reach the VIH spec when the device is operated at 5V Vcc.

    You could consider using a device specially designed for up-translation like the SN74LV1T34 or SN74LV6T17. Alternatively, you could use an open drain buffer like the SN74LVC2G07 and pull-up resistors on the outputs to achieve up translation.