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Thread: TeensyLC supply voltage range

  1. #1
    Junior Member
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    Feb 2018
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    TeensyLC supply voltage range

    I must have searched the wrong terms since I can't imagine I'm the first to ask the question. According to the data sheet the processor in the TeensyLC can operate from 1.7 to 3.6V Vcc.

    https://www.digikey.com/product-deta...FT4-ND/4234818

    I found reference to supply voltage ranges for other Teencys here but nothing about the TeencyLC
    https://www.pjrc.com/teensy/external_power.html

    I want to communicate, over I2C, with a 2.8V sensor (VL53L0X) . I think there is a trace on the bottom of the TeensyLC that connects the USB Vcc to the Vin pin. Is there a problem with cutting that trace and connect 2.8V to Vin?

    I think that the 3.3V supply on the TeencyLC board will not work.

    Will there be any other problems?

    If this works will I be able to connect the SDA, SCL Xshut and GPIO pins directly between the VL53L0X and the TeencyLC?

    Even though the SDA and SCL may be 3.3V tolerant (according to some sources) it appears that XShut is not. A really clean design would include level shifters but If I understand correctly I can eliminate all of that if I can run the TeencyLC at 2.8V

    Thanks in advance for any help you can give.

  2. #2
    Senior Member+ Theremingenieur's Avatar
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    A look onto the Teensy LC schematics (on the PJRC website) that Vin (and Vusb as long as the trace isn‘t cut) are going to the CPU‘s internal voltage regulator which will then output the Vdd (normally 3.3V) for the CPU and the MKL02 boot loader chip.
    After cutting the Vusb to Vin trace, you have several options:
    1) Feed a voltage high enough into Vin, so that the voltage regulator might output stable 3.3V (not needed in your case)
    2) Feed nothing into Vin to disable the voltage regulator and feed the desired regulated CPU voltage directly into one of the 3.3V pins. This voltage might be lower than 3.3V, just make sure that it is high enough to make the CPU and the MKL02 run without problems. 2.8V should be safe.

  3. #3
    Junior Member
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    Feb 2018
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    Thank you for your quick and clear reply.
    I will try it.

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