Teensy 4.1 Not Working or Registering USB?

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David1983

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Hi,

I was working on a project using the teensy 4.1 when all of a sudden my teensy 4.1 stopped working with USB power. Particularly, I'm noticing that:

1. the IDE doesn't register a teensy being present in any port
2. the 3.3V pins read 0.65V despite the 5V pin reading normally
3. The USB port gets really hot whenever the USB gets plugged in.

What I'm wondering is what could've caused this. I'm still fairly new to microcontrollers and I was in the middle of making some pretty major changes when I noticed this. The parts that I'm particularly suspect of are:

1. The PowerBoost 500C that I'm using to power my project. I'm not sure if I wired this incorrectly but I attached the 5V and GND to the rails of a prototype board and then connected the VIN of my teensy onto the 5V power rail too. Could this have been too much power (the PowerBoost actually sends 5.2V out of the 5V pinout).

2. I soldered a component directly onto the 3.3V and a GND pin on the teensy but I made sure that there were no connections between the 5V and 3.3V pin both with a magnifying glass and a desoldering braid. Even so, I think that's the most likely culprit as from what I understand, 5V power into the 3.3V pin automatically kills the teensy.

3. Other components I used might've caused a short in the circuit or other weird behaviour but I doubt it given that I've been working with these sensors and am pretty confident I wired them correctly. I used a MAX31856 and MMA8451 along with a custom microphone and aside from that just some LEDs and a button. I'm again fairly certain there are no shorts present on the prototype board as I didn't see any solder bridges and I had successfully retrieved data before but still.

I don't expect people to necessarily know what caused the issue, but any input on how I can avoid this happening again would be appreciated. Also confirmation that the circuit is indeed broken would be helpful I guess. :(
 
I can confirm 5.2V is perfectly fine for VIN & VUSB, as long as there isn't a large spike above 6V during startup.

2. the 3.3V pins read 0.65V despite the 5V pin reading normally

I'm sad to say 0.65V is a pretty bad sign, likely hardware damage. When 3.3V power measures only millivolts and the regulator gets hot, usually the problem is solder or other metal shorting the power somewhere. But when the "short" is about 0.6 to 0.7 volts, the short is usually damage inside one of the chips.

The first step is to disconnect all the external circuitry, just in case the problem is happening outside of the Teensy board.
 
Yeah I found another thread that discussed a somewhat similar scenario and that's what it sounded like. I disconnected everything and the issue still remains... oh well, onto the next board I guess. Is this the type of damage that occurs randomly though? What could've caused such hardware damage?

Thanks for the response by the way!
 
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