Teensy 3.1 3.3V pin actual voltage

[amundsen]

Hello,

On my Teensy 3.1, when the board is powered by the USB port, I measure between 4.05V and 4.07V on the 3.3V pins. Is it normal?

 

[PaulStoffregen]

No, that's definitely not normal. Something is wrong!

 

[amundsen]

So how can I solve this?

 

[Cosford]

When you're measuring this voltage, is the Teensy connected up to external circuitry?
If this is the case, disconnect the teensy from anything else (apart from the USB cable of course) and remeasure the voltage.

I suspect it's something in your external circuitry trying to drive that pin to that voltage.

 

[amundsen]

When you're measuring this voltage, is the Teensy connected up to external circuitry?
If this is the case, disconnect the teensy from anything else (apart from the USB cable of course) and remeasure the voltage.

I suspect it's something in your external circuitry trying to drive that pin to that voltage.

The Teensy was only connected to a Sparkfun Teensy-to-XBee adapter but (happily) without the XBee being plugged onto it. Also, with the same adapter and a Teensy 3.2 there was no such issue.

Also, the same voltage was measured with the 3.1 unconnected to the SparkFun adapter. So my circuit is not the issue here I guess.

Could it be a defective unit?

 

[PaulStoffregen]

Can you unplug it from that Sparkfun board and test with only the USB cable?

 

[amundsen]

Can you unplug it from that Sparkfun board and test with only the USB cable?

That's what I did (see my latest post) and the measurement was the same.

 

[Ben]

That Teensy seems to be defective
But it's not completely unusable, I think you can still use it with an external 3.3V regulator if you can somehow prevent the 5V from reaching the teensy's pin (cut a trace on the board).
Ben