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Thread: TeensyPico- Miniaturization of Teensy 4.0 Board - 12x12mm Teensy board as QFN package

  1. #1
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    TeensyPico- Miniaturization of Teensy 4.0 Board - 12x12mm Teensy board as QFN package

    Hello Paul, Hello Teensy fans,

    We have the idea to put most of the components of the Teensy 4.0 or Teensy 3.6 board in a small package (Embadded QFN or BGA Chip). This way, in case of projects that require miniaturized electronics, the standard Teensy board can be used for development and the embedded chip (system in package) can be placed on the PCB of the final product. This will be the smallest arduino compatible board ever!

    Here is a photo of a similar embedded module or System in Package:
    https://www.izm.fraunhofer.de/de/abt...hnologies.html


    Fraunhofer IZM is the world's leading institute for the integration of robust and reliable electronics and we can develop and manufacture the System in Package in our institute. We would be happy to send you some samples of the System in Package and share the design files with pjrc once we are ready.

    We need pjrc's help with the teensy board and getting the components.

    Could you please send me an official quote to purchase 500 pieces of the following components (for each of Teensy 4.0 & Teensy 3.6):
    MCU, bootloader chips and crystals.

    Could you provide the BOM list (e.g. mouser or digikey links) of the Teensy 3.6 & Teensy 4.0 boards?

    Do you perhaps have an Altium or Eagle schematic and layout files of both boards that you can provide?

    Once we have decided whether to miniaturize the Teensy 3.6 or 4.0 board, I will post the final reduced schematic for discussion.

    I would appreciate feedback from others interested in this project

    Thanks ,
    Basel Adams

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    Here is a photo from another project:

  3. #3
    Senior Member blackketter's Avatar
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    Very interesting, though the photo didn't make it...

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  5. #5
    Senior Member PaulStoffregen's Avatar
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    Before we go too much farther, I have 2 questions about the feasibility of this project.

    1: For a 12x12 mm size, even if you have 2 sides each with 144 sq mm surface, how will you fit in the parts which normally takes about 500 sq mm?

    Click image for larger version. 

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    Just the IMXRT chip is 100 sq mm, the flash memory is 6 sq mm, and the bootloader chip is 9 sq mm.


    2: How will power dissipation work? Running at 600 MHz, a Teensy 4.0 typically uses about 100 mA. Can this 12x12 mm package with another layer of insulating material really dissipate 0.5 watts? What is it's thermal resistance? (or how much additional temperature rise can be expected in the IMXRT chip?)

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    2: How will power dissipation work? Running at 600 MHz, a Teensy 4.0 typically uses about 100 mA. Can this 12x12 mm package with another layer of insulating material really dissipate 0.5 watts? What is it's thermal resistance? (or how much additional temperature rise can be expected in the IMXRT chip?)[/QUOTE]

    you are right Paul, for a TLC probably not a big worry but for T36 and T4 very big worry - i would not even
    try it without doing at least a rough 3D thermal simulation first.

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    > even if you have 2 sides each

    Seems to me that with 3D, you could have 4 sides x 144 mm˛ = 576 mm˛.

    Thermally, one could put the IMXRT chip on the top. But it's not clear to me that encapsulation doesn't sometimes improve heat transfer.

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    Very good points. Thank you!

    1. Point One:
    12x12x3mm would be our target, but this is not completely fixed. We can make the system in Package (sip) a bit bigger if this would reduce the production cost (if we reduce the number of sides / planes).

    We can achieve this by doing following:
    - We can use 3 sides (embedded double assembled PCB in the middle of the sip and components on the top) or even 4 sides (two double assembled PCBs on top of each other) with 144 mm˛ each side
    - Reducing the Schmeatic to the minimum. (no USB port (a docking station can be used for programming), no push button etc.)
    - By using of smaller components (e.g. 0201 passive components)

    In the case of the Teensy 3.6 with less componants, we could achieve the system in Package with components on only two sides, which could reduce the production costs

    2. Point two

    That would be an issue, that is why I was thinking of Teensy 3.6 (@180MHz) and not Teensy 4.0 for the beginning
    We have many methods in our institute to solve the thermal management problem. We have already built many SIPs that even contain power components. The "through contacts" inside the system in package help to improve heat transfer. Here are some actions we can take to address the thermal issue:
    - Mounting the critical components on the top of the system in Package rather than inside it.
    - Using thermal paste/underfill for the components that get hot
    - Additional vias
    - Limiting the top CPU speed if necessary.

    I'll share latter some information about thermal resistance inside the SIP later, and I'll do some thermal measurements with Teensy boards I have here.

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    yes- if you could put the cpu and the regulator on top (like the photo you have of the imaging chip
    on top) with its upper surface exposed that would help a lot. we did some thermal imaging of a
    Teensy 4.0 at 600 MHz and found that the top of the cpu and the top of the regulator were
    within 2 degrees of each other.

  10. #10
    Senior Member PaulStoffregen's Avatar
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    The MK66FX1M0VMD18 chip on Teensy 3.6 is much larger, 13x13 mm. It's also out of stock and (so far) we don't have a clear time frame when more will become available. Even if we do get more soon, PJRC probably will not be able to spare any of those chips. If you choose to go that route in this time of global chip shortage, you'll be on your own for trying to buy that chip.

    The IMXRT1062DVL6B chip on Teensy 4.0 is 10x10 mm. If this project happens in the remainder of this year, or in early 2022, PJRC can provide 240 of those chips. Sorry, we can't allocate 500 for you. I believe this is a really interesting project and I want to help you, but we just can't spare more than 240 pieces in this time of chip shortages.

    Plenty of bootloader chips are available for either path.

    The chips are packaged on JEDEC trays. We don't have these parts on tape & reel.

    We might be able to provide the Winbond flash chip, if you're unable to buy them. Those are on reels.

    For all the other parts, you will need to source them elsewhere. For this sort of miniaturization, you'll probably need to find smaller versions.

    If the 5V to 3.3V regulator is kept in the design, perhaps you could help with the thermal performance by redesigning to use an efficient step-down buck regulator? The main 2 technical requirements are an active high enable pin with on threshold of 1.0V or less, and active discharge of the output voltage when disabled. Many modern parts offer these features, but do check the enable pin logic high threshold. Some chips have a 1.2V spec, which should not be used.

    Most of the resistors and capacitors can use reduced size parts. But be careful of shrinking the 4.7uF capacitors which are 0402 size. All of those capacitors have only their full rated capacitance when the voltage is near zero. When you charge them up with 3.3V or even 1.25V, their effective capacitance decreases. That effect tends to become much worse in physically smaller sizes.

    It is critically important to place some of the smallest decoupling capacitors directly underneath the BGA chip. The capacitors for the input and output of the chip's built-in 3.3V to 1.25V DC-DC converter also need to be placed directly underneath. Longer traces will cause a lot of extra noise and might even cause the design to fail. Placing all the parts on only 1 side is pretty much out of the question. Those capacitors must be directly underneath the BGA!

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    Quote Originally Posted by PaulStoffregen View Post
    The MK66FX1M0VMD18 chip on Teensy 3.6 is much larger, 13x13 mm. It's also out of stock and (so far) we don't have a clear time frame when more will become available. Even if we do get more soon, PJRC probably will not be able to spare any of those chips. If you choose to go that route in this time of global chip shortage, you'll be on your own for trying to buy that chip.

    The IMXRT1062DVL6B chip on Teensy 4.0 is 10x10 mm. If this project happens in the remainder of this year, or in early 2022, PJRC can provide 240 of those chips. Sorry, we can't allocate 500 for you. I believe this is a really interesting project and I want to help you, but we just can't spare more than 240 pieces in this time of chip shortages.

    Plenty of bootloader chips are available for either path.

    The chips are packaged on JEDEC trays. We don't have these parts on tape & reel.

    We might be able to provide the Winbond flash chip, if you're unable to buy them. Those are on reels.

    For all the other parts, you will need to source them elsewhere. For this sort of miniaturization, you'll probably need to find smaller versions.

    If the 5V to 3.3V regulator is kept in the design, perhaps you could help with the thermal performance by redesigning to use an efficient step-down buck regulator? The main 2 technical requirements are an active high enable pin with on threshold of 1.0V or less, and active discharge of the output voltage when disabled. Many modern parts offer these features, but do check the enable pin logic high threshold. Some chips have a 1.2V spec, which should not be used.

    Most of the resistors and capacitors can use reduced size parts. But be careful of shrinking the 4.7uF capacitors which are 0402 size. All of those capacitors have only their full rated capacitance when the voltage is near zero. When you charge them up with 3.3V or even 1.25V, their effective capacitance decreases. That effect tends to become much worse in physically smaller sizes.

    It is critically important to place some of the smallest decoupling capacitors directly underneath the BGA chip. The capacitors for the input and output of the chip's built-in 3.3V to 1.25V DC-DC converter also need to be placed directly underneath. Longer traces will cause a lot of extra noise and might even cause the design to fail. Placing all the parts on only 1 side is pretty much out of the question. Those capacitors must be directly underneath the BGA!

    Thanks for the tips.

    Okay, Teensy 3.6 is no longer an option then. What about Teensy 3.2. Can you provide us with MCU and bootloader chips?

    If we go for the Teensy 4.0. 240pcs would be fine for us. Jedec trays are not a problem. It would be nice to have the flash chips on reels.

    I talked to my colleagues about the thermal issue. According to our experience with other project, the system in package would improve the thermal characteristics of the board.

    I am looking forward to your offer for the Teensy 4.0 Bootloader, MCU & Flash Chips. Maybe also for the Teensy 3.2. You can mail the offer to me at: basel.adams@izm.fraunhofer.de

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    Quote Originally Posted by analog&RFmodels View Post
    2: How will power dissipation work? Running at 600 MHz, a Teensy 4.0 typically uses about 100 mA. Can this 12x12 mm package with another layer of insulating material really dissipate 0.5 watts? What is it's thermal resistance? (or how much additional temperature rise can be expected in the IMXRT chip?)
    you are right Paul, for a TLC probably not a big worry but for T36 and T4 very big worry - i would not even
    try it without doing at least a rough 3D thermal simulation first.[/QUOTE]

    The thermal conductivity of prepreg of the System in Pakage is about 1W/m*K. That of standing air is much worse (0.026)
    Should be unproblematic with a consumption of 100mA...

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    Senior Member fdaniels's Avatar
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    Im in for the 3.2 version - would save me a lot of hassle in my modules.....

  14. #14
    What a really nice idea. I moved from Arduino to Teensy because the Teensy boards are smaller and faster, but it would be really nice to have the whole board as big as a chip you can put on the PCB. @Pjrc: are you planning to add this to your product portfolio?

  15. #15
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Matteo Maisto View Post
    @Pjrc: are you planning to add this to your product portfolio?
    At this very early stage, any plans could at best be described as "wait and see how this turns out".

    Right now, PJRC's only involvement is limited to providing up to 240 chips (which otherwise would have been soldered to Teensy 4.0 circuit boards) and answering questions on this forum thread.

    If you need a module format, at this point MicroMod Teensy is your best path. The physical size is approx 4X larger. But it has the advantage of actually existing today... you can buy them right now from Sparkfun and some distributors, and plenty (or at least 250 - probably many more) are in stock today.

    MicroMod Teensy also as the advantage that you can build your own PCBs with an inexpensive socket. If you build a small production run of a few hundred products which you intend to sell, those cheap sockets can really help reduce your up-front capital investment. Then you can buy the modules as you make actual sales. Many would-be tech entrepreneurs make the mistake of trying to minimize total cost, when what usually matters is minimizing financial risk and managing cash flow. MicroMod Teensy, or regular Teensy plugged into through-hole sockets, can really help in that regard.

    Even if this much smaller 12x12 module turns out to be wildly successful on every technical level, whether it would be a viable business model for PJRC to make and sell them remains to be seen. Hypothetically, partnering with another company to make & sell the modules, as we do with Sparkfun for MicroMod Teensy, might make more sense than spreading PJRC's limited resources across more products.

    Still, a 12x12 mm module is exciting.

  16. #16
    Senior Member PaulStoffregen's Avatar
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    @Badams - As you continue working on this, please keep in mind Teensy 4.0 has 11 test points.

    Click image for larger version. 

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    These 11 points are indicated on the schematic.

    Click image for larger version. 

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    Last edited by PaulStoffregen; 10-27-2021 at 12:02 AM.

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    PJRC tests every Teensy 4.0 using all of the I/O pins and these 11 special test points.

    For a visual idea, here are the pogo pins which mate with Teensy 4.0 during the test.

    Click image for larger version. 

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    Maybe you won't need all of this for testing these modules? Maybe it could be considered overkill by some people, but Teensy is used by so many different people for such a wide range of projects that PJRC goes to a lot of effort to makes sure every Teensy is thoroughly tested.

    If you use less than these 11 test points, I hope you will put some careful thought and design into how you will test these modules.

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    Hello Paul,
    I plan to build the first board with the reduced schematic and small components on an eva PCB with all 11 test points. I will use this board for the electrical evaluation. There will be no space for all the test points on the final embedded module (SIP).
    Which of the test points are the most important?
    What are the expected outputs from the test points?
    Could you please answer my questions regarding Teensy 3.2 and the official offer for the Teensy 4.0 chips?

    Thanks!
    Basel

  19. #19
    Senior Member PaulStoffregen's Avatar
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    PJRC can't supply the MK20 chips normally used for Teensy 3.2 for this project. They're also much larger. Refer to the datasheet for details and don't forget to account for whatever PCB footprint you will use.

    On Teensy 4.0, you won't need to 2 test points for the bootloader. The other 9 test points are all related to power. To understand this, please refer to "Power Up Sequence" on the T4 bootloader chip page. Use the javascript buttons to see the overlay on the schematic of how the power is brought up. Also look for the "Hardware Development Guide for the MIMXRT1050/MIMXRT1060 Applications Processor, Rev.0, 08/2018" link on that page for NXP's guidelines.

    Aside from just checking that every part of the chip powered up correctly, the test points allow for discharging the capacitors. Depending on how you plan to test, this may or may not matter. The PJRC test process rapidly powers the board up and down (fully discharging all capacitors) many times over about 100 ms, using different combinations of the power and ground pins, so we can be sure all of them work properly. The capacitor discharge is done by 100 ohm resistors and N-channel mosfets, which allows for safely clearing stored charge in only milliseconds. Again, you may or may not need this. It's really up to you.

    Likewise for the many choices you will need to make about modifying the design, I can answer some questions here on the forum, but you really need to do the engineering work behind those choices. I'm not going to get that directly involved in this project. You need to do that work based on an understanding of the design.

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    Alright. Thank you very much Paul. We will go then for the Teensy 4.0

    The TLV75733p voltage regulator chip is out of stock. Can we buy it beside the MCU, bootloader and flash chips from PJRC (240pcs each)?

    I am going to do big changes in the orginal TS4 schematic. Just replace some of the passive componants with smaller ones and remove following componants:
    - USB port
    - Momentary push button
    - Reverse polarity protection: dmg2305ux
    - 500ma fuse
    - 32.768kHZ Crystal

    Any suggestions for other components I can get rid of?

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    p.s. What are the part number of the crystals & ferrits used in the TS4.0?

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    As I mentioned before, we will use the MCU used in Teensy 4.0 (mimxrt1062dvl6a). We are thinking about routing/offering more pins out of the QFN embedded module (namely some the pins used in Teensy 4.1 and not in Teensy 4.0 , e.g. Ethernet pins and additional Gpios)
    Would those pins get supported by the Teensyduino?
    Last edited by Badams; 11-05-2021 at 05:05 PM.

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