I have a problem with the teensy 4.1 module, almost all of our damaged modules have problems with the u2 and q1 ICs when the thermal part is hot and when connected to the laptop the port is not read and there is no power input even though the boot button is pressed there is no response indicating the module can turn on. There are already about 5 damaged modules there, we are having difficulty finding components in our country, Indonesia. Can you recommend the components and complete specifications? We really hope to get a reply. Then what is the function of the q1 IC? I initially felt it was a regulator but it seems it was a p channel for switching. And what is the u2 IC serial IC for reading ports?
Problem in Teensy 4.1
- Thread starter Zeann
- Start date
PaulS
Well-known member
Do you see these problems with bare Teensy 4.1's or are they connected to other electronic circuits?
A Teensy does not have a Boot button, only a Program button.
A fresh Teensy from the factory contains the Blinking program (flashing the onboard LED).
Q1 is acting a an "ideal diode". U2 is the Bootloader chip, nothing to do with serial IC for reading ports.
I suggest to study the Teensy 4.1 page and the Bootloader page thoroughly - it may answer your questions and help to debug the problems you see.
Regards,
Paul
A Teensy does not have a Boot button, only a Program button.
A fresh Teensy from the factory contains the Blinking program (flashing the onboard LED).
Q1 is acting a an "ideal diode". U2 is the Bootloader chip, nothing to do with serial IC for reading ports.
I suggest to study the Teensy 4.1 page and the Bootloader page thoroughly - it may answer your questions and help to debug the problems you see.
Regards,
Paul
Rolfdegen
Well-known member
If you are experiencing USB power issues on Teensy 4.1 and Teensy 4.0, use an external +5V power supply connected to the Teensy Vin pin. However, be careful: the USB Vin wire must then be cut with a utility knife (see image). Do not overload the Teensy 3.3V connection with any other circuit. The maximum current is 250mA.
For development on the Teensy, I always use a USB2.0 isolator—for example, this one here : ISO-U20
This protects the Teensy from overvoltage
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Denis Bélières
Active member
Some time ago, I put on the forum another question wich did not received any answer. If the board is powered by an external 3v3 source, with the above connexion opened, what happens when the power is off while a computer is connected to the USB port, there maybe some voltage on the two USB input with no power on the chip ... Is that dangerous ? And if the connexion is not cut, then the poor 3V3 regulator TLV75733 will power my whole system and get down on his knees because current will be too high. But I suppose that USB standard is such than anything not powerd may stay connected to a computer : such is the case for a printer ...
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Denis Bélières
Active member
But I do not want to have two power supplies ; one 5 V for teensy, and one 3V3 for peripherals which do not withstand 5 V... It is far simpler if my whole logic system is powered with only one supply ! I have yet an unregulated +18V from a lithium battery to a step motor, then a first step down switching regulator to provide +12 V to a DC motor, and then another to +3V3 to logic circuity.
By the way, with a +5V power supply connected to Vin, and an opened jumper between Vin and USB power, the problem is exactly the same ! When this +5V is switched off, does the IMXRT chip withstands USB signals from the USB connector ? What happens if you cut +5V power supply during an USB transaction ? Normal CMOS input pins doesnot withstand voltage above power supply (zero !) excepted if current is limited in the internal protection diodes of the chip. What can source the computer USB data signal if they are shorted to groud in thes protection diodes ?
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Teensy is simply not intended to be powered from 3.3V alone, there are some pins (on the MCU, not the PCB) which expect 5V.
Denis Bélières
Active member
Yes indeed, without 5V the internal USB drivers won't work. But the data sheet (not reference manual) says that the VBUS pins can be left not connected when not used. So the chip can be powered with 3V3 and other lower voltages derived from 3V3, and +5V supplied by USB connector only when in use (aforementioned jumper not open). Then the only problem is that Teensy's 3V3 regulator will be in parallel with external 3V3.
Denis Bélières
Active member
Do I need SNVS ? I am not concerned with Real Time Clock, protections, keys, security ... And diode D2 routes +3V3 to VDD_SNVS_IN.
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Denis Bélières
Active member
Many thanks for these enlightening explanations. I saw in IMXRT manual that power up sequence was somewhat complicated, and thought that there was adequate things on the board, I did not try to analyse things further as you do there. Maybe the connexion of some VBAT supply is the simplest solution, but I don't like any connexion outside of a regular 28 pins DIL socket (I am using Teensy 4.0). So, now, I am defeated
, I will change my schematic to provide a +5V supply, but this complicates the routing on my PC board (gerber files were ready to send to JLCPCB) ... Perhaps it will be interesting (at least for me ) to put a new Teensy 4.2 on the market, working with a +3.3V supply ...
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Hopefully you are planning on using a different name before you go to marketPerhaps it will be interesting (at least for me
jlaustill
Member
This is a major issue for small batch custom electronics. Why must the world of EE insist on shipping something different than used in development haha. I love the idea of a teensy 4.2 @Denis Bélières , especially if it pins out the USB connector so I can stop cutting a usb cable and soldering the wires to my carrier board blah, and just including the "optional" diode so you don't have to worry about using 5V Vin and USB at the same time would be great too. Little things like that make for major quality of life improvements, for me at least
Denis Bélières
Active member
I do not intend to develop anything except gadgets in my garage ... That's far enough for my old white-haired dome ...
PaulStoffregen
Well-known member
Maybe consider using MicroMod or Lockable MicroMod. It is designed for 3.3V power input.
To explain the tech side, NXP's chip has complicated power startup requirements. It's documented on the T4 bootloader chip page. Scroll down to "Power Up Sequence".
The requirement for higher than 3.3V versus direct 3.3V comes at step #6. On Teensy 4.0 and Teensy 4.1, a LDO voltage regulator receives the PMIC_ON_REQ signal at its enable pin. So the minimum input voltage is determined by that voltage regulator's low (but not zero) dropout voltage.
MicroMod has a pair of mosfet transistors rather than a voltage regulator. When PMIC_ON_REQ asserts, the 3.3V power is passed directly by a P-channel mosfet with low on resistance. Look on the upper left part of the schematic for details.
NXP also documents all this stuff in their datasheet, a hardware design guide, and some app notes. Life would have been easier had they designed their chip to just take 1 power input and it would do all the rest automatically. But that's not the silicon they made. The chip implements a large number of features, including a number of security features. The chip designers chose this approach because they needed a way to meet all those requirements. They too were probably under some constraints, as adding analog circuitry in a new generation of chip costs more design time and higher risk compared with purely digital circuitry. Unfortunately, choices NXP's engineers made do mean the chip has this complicated startup process. In the design of Teensy, I tried to make it as simple as possible, but only so much could be done (at a reasonable cost and fitting in the small form factor).
To explain the tech side, NXP's chip has complicated power startup requirements. It's documented on the T4 bootloader chip page. Scroll down to "Power Up Sequence".
The requirement for higher than 3.3V versus direct 3.3V comes at step #6. On Teensy 4.0 and Teensy 4.1, a LDO voltage regulator receives the PMIC_ON_REQ signal at its enable pin. So the minimum input voltage is determined by that voltage regulator's low (but not zero) dropout voltage.
MicroMod has a pair of mosfet transistors rather than a voltage regulator. When PMIC_ON_REQ asserts, the 3.3V power is passed directly by a P-channel mosfet with low on resistance. Look on the upper left part of the schematic for details.
NXP also documents all this stuff in their datasheet, a hardware design guide, and some app notes. Life would have been easier had they designed their chip to just take 1 power input and it would do all the rest automatically. But that's not the silicon they made. The chip implements a large number of features, including a number of security features. The chip designers chose this approach because they needed a way to meet all those requirements. They too were probably under some constraints, as adding analog circuitry in a new generation of chip costs more design time and higher risk compared with purely digital circuitry. Unfortunately, choices NXP's engineers made do mean the chip has this complicated startup process. In the design of Teensy, I tried to make it as simple as possible, but only so much could be done (at a reasonable cost and fitting in the small form factor).
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Denis Bélières
Active member
Thanks for explanations. Maybe for another project I will turn to MicroMod, but now for the current one it is too late to change. I just changed my 3v3 regulator for a 5V one, and took 3V3 from Teensy to power some peripheral (current is Ok). All this is just a gadget for fun (animated snake poping out of a box when I play music ...). Paul, did you download https://www.dropbox.com/scl/fi/45sk...ey=japjdwhltmwjzjv3g114azk4j&st=ofjwo9va&dl=0 ?