Broke my Teensy 4.1? IXMRT not booting...

I

internett

Member
Hi all,

my Teensy 4.1 is not longer starting, only connected to USB. Nothing else is connected. Measured all Voltages for the booting process (8 steps) but from step 4 the Voltages are to low or zero:
1) USB_VBUS = 5V
2) VDD_USB_CAP = 2,5V
VDD_SNVS_IN = 2,3V
3) VDD_SNVS_CAP = 1,1V
so far so good, then it starts lower:
4) NVCC_PLL = 0V
VDD_HIGH_CAP = 0,54V
5) PMIC_ON_REQ = 1,75V
6) 3V3 = 0,54V
7) R6 High side = 0V
8) VDD_SOC_IN = 0V

as descibed in PowerOn step 4 IMXRT should turn on PLL and Analog regulators. Is the IMXRT power part broken or what is going wrong? How to proceed to find the Error?
Thanks in advance for your support,
Greetings ...
 
Are there any hot components?
Was it connected to anything before? In use for any good time before that?
 
Hi,

no hot components. It draws only 28 µA. Normally it needs 65mA or more to run
Yes it was connected to several components:
2 power supplies (1x 3,3V to vBat, 1x 3,3v to 3,3v rail to startup without 5V), I2C1 several components and a 4" display.
It broke after loading up a new program by USB (unfortunately left USB connection for some time for serial output). Tested with a running Teensy it draws approx 180mA over the USB. I assume it powered back the power supplies drawing to much from USB, but the fuse is still fine (see post#1)
 
Does a 15 second Restore press of the PGM Button until the USB end RED LED gives a flash to release do anything?

That ideally would restore a factory Blink sketch.
 
The 3.3V has only 0.54V so the LED will not blink, even the blink sketch can be restored. the startUp process of the IMXRT stucks in step 4 (see post #1)
Therefore i need to know which part is broken and i have to replace, to get the Teensy back to live.
 
You're not supposed to supply 3.3V directly to the teensy because it may backfeed into the 5V->3.3V regulator and kill it, which sounds like exactly what has happened.
 
Yes I know. The regulator isn't the problem. switched it and the problem is still the same.
Need to know what exactly is broken to switch it.
 
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