2nd teensy -> smoked. Everything was double checked. Serious issue here.

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ddmods

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So, I killed my first teensy. That was my fault. Second one I used the correct pin(double checked output @5.1v) Hooked up to vcc and ground. Chip smoked.
This project works fine until I try to power the teensy via VCC, then it's smoked. Any idea on this? It's only 5.1v going to Vcc.
 
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Where is the voltage coming from? Is it a regulated output?
As an example, sometimes people use ATX power supplies where the nominal 5V rail is not well regulated and can have transient spikes well above 5V.

Also, looking at the pinout here
http://www.pjrc.com/teensy/pinout.html
by VCC you do mean the top pin labelled Vin (3.7 to 5.5) and not any of the others (3.3V, Vbatt).

When you apply 5.1V, is the Teensy also getting power over USB or not?
 
Hi, yes, Vin pin sorry.. The one that says 3.7-5.5v in the picture. I was a bit frustrated earlier. Should have waited to post. I'm using an LM317 and it's outputting 5.1v how I have it setup. I have an arduino I might use for the project, since I can just power it and it works. I'm going to have to cheese the display and other things to cut down on the code..

EDIT: I really made sure everything was perfect this time. I'm using an lm4040 2.5v for voltage reference on aref. I uploaded my code and set the analog reference to external then soldered the lm4040 up. plugged in again and everything was fine. Cut the Vusb trace(double checked trace was gone with a DMM) and put pin headers in the Vin and Gnd pins. Put batteries in and Mk20 started smoking.

I also had the display wired for hardware SPI(was working fine) and some analog inputs using voltage dividers. Double checked the voltage on those as well before powering the teensy via the Vin pin. They were below 2.5v.
 
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So to confirm

(1) when you have the batteries (which I assume is what you are powering the LM317 with- you were not quite explicit) REMOVED, and the USB connected to the teensy, nothing is lighting up? I ask because I had made the mistake of cutting the wrong trace when I thought I had cut V_usb. I noticed because without my battery and with the USB cable, my teensy led flashed.

(2) You have the ground from the LM4040 connected to the ground of the teensy? I'm not 100% on this and don't know whether Aref-ground is sufficient, but I know generally two voltage sources you want to have the grounds sorted out [though the LM4040 isn't much of a current source]

(3) You have tested the 2.5V output of the LM4040? I ask because the LM4040 has higher voltage modes like 4V+


Sorry to hear you've been blowing teensies. That can be a really frustrating (and quickly $$) experience. For what it's worth if you're buying a bunch of these, OSHPark has them for about $2-3 cheaper than anywhere else (and they're genuine, of course.)
 
1. I am powering the lm317 via batteries and even have a Pfet before it for reverse polarity protection. I for sure cut the correct trace. I didn't plug a usb cable into it after the initial programming and making sure everything was working correctly, only double checked that the trace was cut.

2/3. Yes, this is the 2.5v version of the lm4040. It's going from aref to agnd. Double checked with my DMM, and it was @ 2.505v. Within specs for the lm4040.

The first one was totally my fault, as I connected 5.1v to a 3.3v pin(the one that says V on the bottom). This one, however, I can't figure out what happened. Since they are $20 each, I took care to make sure it was wired properly. I really don't want to buy another one. There's nothing I could do differently. If PJRC had the mk20 with the bootloader on it for a decent price, I would replace it then test it again.
 
I don't know what happened here (causing the damage), but I can tell you Teensy 3.1 does work with 5V power properly applied to VIN & GND.

MANY projects have been built this way, with the VUSB-VIN jumper cut and 5V power applied. Here's one we made a few months ago for Freescale at Maker Faire.

http://community.arm.com/groups/embedded/blog/2014/05/23/led-video-panel-at-maker-faire-2014

The 4320 LEDs and the Teensy 3.1 are powered by six 40 amp, 5V power supplies (yes, a total capacity of 240 amps). If you play the video on that page, a close-up of the Teensy appear around 0:23. Those red and black wires are from the power supplies on the back side, powering the Teensy. No USB cable is used.


If PJRC had the mk20 with the bootloader on it for a decent price, I would replace it then test it again.
Click to expand...

These are really intended for building a board from scratch, but indeed the chip with bootloader is available.

http://www.pjrc.com/store/ic_mini54_tqfp.html
 
Do you have any clean photos from the 2nd setup that blew? Maybe something would stick out.

Bear in mind it's pretty hard to solder these chips. Most hobbyists couldn't with a basic iron, though if you have the tools and experience you can.
 
If you mail the dead one back (the one that died mysteriously), I'll take a look. Not sure if I can do anything, but since this has been so much trouble (and even more trouble to mail the dead board), at the very least we'll give you a 30% discount if you want to buy a replacement.

Edit: if you send it back, please print a copy of this thread (1st page is fine) and put the paper in the package. Without a way to link it back to this thread, it'll just be some random returned board with unknown history.
 
I'll totally do that. :) Thanks! I'm comfortable enough with soldering to replace the kd20 QFP, if that says anything. I've done everything from QFP to BGA rework. I already desoldered everything getting ready to add the arduino to the project or I would take a picture. I really appreciate the help. Sad day for me being a nerd...
 
I really appreciate the discount, too! I would really like to use the teensy for my project. I'll actually record and take pictures of absolutely everything when I get it, hoping it could help someone else. Going out tomorrow.
 
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