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Thread: Boot on Power-Up Problem with three T3.6s.

  1. #26
    Junior Member
    Join Date
    Feb 2016
    I've posted to this old thread as I just had a problem with power-on for a teensy 3.6 and looked for other comments.

    I was using a small switching regulator based on an MP2307. These are available for pennies on ebay and are pretty efficient as they use synchronous rectification. They also offer soft-start which is a bonus .. but the boards I have follow the data sheet recommendation and take 15ms to start (a nice clean linear ramp). I found I had to reset the board manually before it would work.

    I've swapped the regulator for an almost equally small and cheap MP1584 device. It starts in 5ms and the teensy boots fine. It would also have been possible to change a capacitor to speed it up.

    I also have a bunch of 3v3 radios (esp2866 and nrf24l01) on the project. Since these take quite a bit of current, they have their own power supply but that means it's possible for them to be powered and not the teensy, or vice versa. This can result in one or the other being supplied power through their I/O pins.

    Is it possible to supply the teensy directly with 3v3, so I can run it off the same regulator ?

    pic : regulator using MP2307 on the left, MP1584 on the right. The MP2307 pcb is the size of a TO220 and I've found them for as little as 2.70 for 10 ! Note that the max input is only 26V though, so a bit tight for 24V systems. The 1584 has a bit more margin at 28V.

    Click image for larger version. 

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  2. #27
    Junior Member
    Join Date
    Dec 2017
    I have had boot up problems with my Teensy 3.6 for some time now. This thread saved the project! ( I installed a TI LP3470-2.93 that you can order free samples of from TI. This IC has a variable reset signal time and a fixed threshold voltage of 2.93V. I used a 0.22uF capacitor to create about a ~500ms delay, which worked perfectly.

    I wasn't able to reproduce my exact problem consistently to measure the start up voltage waveforms unfortunately. I did have this problem semi-regularly when the teensy 3.6 was exposed to temperatures below 40F.

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