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Thread: T3.6 & T4.0 Schematic question

  1. #1
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    T3.6 & T4.0 Schematic question

    I was looking at the schematics of the T3.6 and the T4.0 and was wondering if someone can help me learn a little bit about them. On both of them I see dots at certain points on the schematic.

    The T3.6 has them on the wiring for both of the usb data lines as well as two at the boot loader chip on pins 14 & 16.

    The T4.0 has even more spots with these dots.

    I have attached the schematics with circles around the dots I'm asking about. Do these dots me that they are supposed to be connected to each other? I'm just trying to learn how these boards work. The main reason why I'm asking is I was trying to figure out how the T4.0 powers up as the mcu controls the enable pin on the voltage regulator, but I don't see any pins on the mcu connected to the 5v from the usb other than the usb vbus.
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  2. #2
    Senior Member+ defragster's Avatar
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    On the product pages (like pjrc.com/store/teensy41.html) read down to the "Test Points" notes in the case of T_4.1.

    You'll see where those names can align with those 'dots'

    For product testing there are small pads as test points to test the function of the circuit for proper function - thos 'dots' are those test points.

  3. #3
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    Ah ok that makes more sense now. Thanks for the explanation.

    I guess that still leaves me with a question unfortunately about how the 4.0 & 4.1 power up. From the schematic the 5v coming in only goes to the voltage regulator and both usb vbus pins. The assumption that I have right now is that when the two vbus pins see 5v the mcu powers up and drives pmic_on_req high? Would this be correct?

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Slapstick View Post
    I guess that still leaves me with a question unfortunately about how the 4.0 & 4.1 power up.
    Maybe "Power Up Sequence" on this page can help?

    https://www.pjrc.com/store/ic_mkl02_t4.html

    Be sure to click the little buttons above or below the schematic...

  5. #5
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    That helps me understand how it works. I didn't scroll down the page far enough prior to see where I could've answered the questions myself.

    Thanks Paul!

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