Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 7 of 7

Thread: 5V clock speed vs 3.3V clock speed

  1. #1
    Junior Member
    Join Date
    Jul 2021
    Posts
    5

    5V clock speed vs 3.3V clock speed

    For a Teensy 4.0, is the maximum clock speed (600MHz) reached at 3.3V or 5V?

    When I read about clock speed in the "Power" section of the Teensy description, it says "Teensy 4.0 has a voltage regulator which reduces the 5V VUSB / VIN power to 3.3V for use by the main processor and most other parts." (https://www.pjrc.com/store/teensy40.html#power) This makes me think that there isn't a need to run more than 3.3V to the board. However, when I read about powering the Teensy from a battery, I read that the maximum clock speed drops when running under 4.5V: https://www.pjrc.com/teensy/external_power.html The table listed in the "External Power" section only lists a max clock speed of 16MHz, so I'm guessing it is old info for the 1.0 or 2.0.

    Thanks!

  2. #2
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    15,274
    Indeed that page is for the older AVR Teensy units.

  3. #3
    Senior Member
    Join Date
    Jul 2020
    Posts
    1,368
    This makes me think that there isn't a need to run more than 3.3V to the board
    The board as is requires 5V power, it cannot accept power on the 3.3V pin without modification: https://forum.pjrc.com/threads/64468...l=1#post259469

  4. #4
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    15,274
    Quote Originally Posted by MarkT View Post
    The board as is requires 5V power, it cannot accept power on the 3.3V pin without modification: https://forum.pjrc.com/threads/64468...l=1#post259469
    Good link @MarkT - didn't have time to note that and find that ref.

  5. #5
    Junior Member
    Join Date
    Jul 2021
    Posts
    5
    Quote Originally Posted by MarkT View Post
    The board as is requires 5V power, it cannot accept power on the 3.3V pin without modification: https://forum.pjrc.com/threads/64468...l=1#post259469
    I saw this and considered doing it; I just wasn't sure if my 4.0's clock speed would suffer for it like the older ones do.

  6. #6
    Senior Member
    Join Date
    Jul 2020
    Posts
    1,368
    No, the processor is 3.3V however you power/modify the board.

  7. #7
    Senior Member
    Join Date
    Apr 2014
    Location
    Germany
    Posts
    9,428
    Quote Originally Posted by MarkT View Post
    No, the processor is 3.3V however you power/modify the board.
    The cpu internally works with a even less voltage - it's adjustable, and the teesy core automatically adjusts it with the CPU speed.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •