SparkFun’s Logic Level Converter


SparkFun has always been good about designing and stocking useful breakout boards. This recently added Logic Level Converter is no exception. It’s uses two BSS138 MOSFETs to shift 5V logic levels to 3.3V. The board handles two separate serial pairs. Just hook up the RX and TX on either side. Provide power at both voltages and the board will happily do the conversion. It’s $2, smaller than the size of a quarter, and perfect for plugging into a breadboard.

Comments

  1. Brian says:

    pardon the stupid question, but will this effectively replace a max232 chip for serial data?

  2. digidelia says:

    negative, the max232 converts TTL serial (0 to 5) to 232 serial (-12 to +12)

  3. DarkFader says:

    A transistor for TX and a voltage divider for RX.
    But it seems like the voltage divider outputs 2.5V, not 3.3V. Close enough though.

  4. Dave says:

    Hmmmn…at the expense of just 1 extra 10K resistor, they could have done 5V -> 3.3V conversion pretty much exactly.
    Adding another 10K in parallel with the top 10K resistor in the potential divider would give the output ratio 10/(10+5) = 2/3. So 5V input would then give 3.33333V out. They claim it also works with 2.8V -> 1.8V conversion. This extra resistor would then give 1.866666V out. Way closer than the 2.5V and 1.6V their design gives out.

  5. charlie says:

    umm … commercial product. no real hack here. i’ll let it slide this time. i like to run my mixed voltage components directly off 3.7 volt lipos. or 5v with some resistors on the 3.3v side. sure it’s “wrong”, but it works for me. i’m not a properly edumacated electricioman, i’m a hacker!

  6. Bryan says:

    A newbie question:
    It says that it could be used for I2C.
    How I could connect, then, the SDA and SCL lines?
    SDA for TX and SCL for RX?

    Thanks in advance. Bryan

  7. ***************

  8. Rina says:

    newbie question:
    It says that it could be used for I2C.
    How I could connect, then, the SDA and SCL lines?
    SDA for TX and SCL for RX?

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