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Thread: Is there a transistor similar to the SN74LV1T125, but the OE (enable) pad is switched

  1. #1
    Senior Member+ MichaelMeissner's Avatar
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    Is there a transistor similar to the SN74LV1T125, but the OE (enable) pad is switched

    I tend to like using Teensys to drive small number of WS2812B's for costumes. In the past, the LC was my favorite Teensy for this purpose due to the built-in level shifter for the A3/17 pin.

    But recently I moved to using the Teensy 4. Both of my previous LC's had solder damage due to heavy usage, and I like the idea of the on/off pin to turn off the Teensy. Originally I was going to VIN, A3/17, and ground connected to a SN74LV1T125 to safely convert the voltage. But I discovered that turning off the Teensy's VIN pin is still active when the microprocessor goes to sleep (which makes sense when I think about it), which meant that the WS2812B's would be left on, unless I specifically turned them off before pressing the on/off button.

    Now it turns out, the WS2812B's that I was using can run at 3.3v, so I just used the 3.3v power (which is cut off when the power shutdown occurs). But not all of my WS2812B's can run at 3.3v. So I was wondering if there was a chip similar to the SN74LV1T125, but instead of OE being set to ground to enable the conversion, I would want OE being set high. Then I could connect:
    • Teensy VIN -> SN74LV<xxx> VCC + LED VCC
    • Teensy 3.3v -> SN74LV<xxx> OE
    • Teensy Ground -> SNL74LV<xxx> Ground + LED ground
    • Teensy A3 pin -> SNL74LV<xxx> A
    • Led DIN pin -> SNL74LV<xxx> T


    What I'm looking for is something in the same form factor (SSOP) as the SN74LV1T125 but OE is inverted. Sure, I could use an inverter chip along with the converter, or more likely just keep using 3.3v, and making sure each LED functions at 3.3v.

  2. #2
    Senior Member+ KurtE's Avatar
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    If memory serves from some of my boards try the SN74LV1T126 like chips... That is 126 is OE and 125 is ~OE...

    There are also chips that have both, I tried one awhile ago that had 4 in each direction (I believe).

    But again remember I am a retired Software guy

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Yup, SN74LV1T126. Logic high on its OE pin causes it to drive its output.

    http://www.ti.com/product/SN74LV1T126

    https://www.digikey.com/product-deta...296-37175-1-ND

  4. #4
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by PaulStoffregen View Post
    Yup, SN74LV1T126. Logic high on its OE pin causes it to drive its output.

    http://www.ti.com/product/SN74LV1T126

    https://www.digikey.com/product-deta...296-37175-1-ND
    Thanks to both KurtE and Paul. I figured there were chips, but I was missing the right search terms.

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