I could try that indeed. I still need to replace the Teensy because it's getting alarmingly hot regardless of whether something is connected to host or not. I also don't know if that's dangerous.
One Component on Teensy 4.1 gets very hot
- Thread starter RobotMan
- Start date
I could try that indeed. I still need to replace the Teensy because it's getting alarmingly hot regardless of whether something is connected to host or not. I also don't know if that's dangerous.
defragster
Senior Member+
If programmed with simple BLINK (No USBHost activation) does anything still get hot? If no hot spots when no USBHost it might point to that switch chip being trashed - and self heating rather than working - and that heating may be causing the other chip to heat feeding current to trashed switch.
Doesn't explain how it got trashed - just that the problem is so far isolated to it to replace or bypass.
PaulStoffregen
Well-known member
With all power off, can you try an ohms measurement from VHOST to GND? Then try again with Teensy 4.1 running a program which doesn't use USB host?
On a good board, the power off measurement should show a gradually increasing number as your multimeter's test current charges the 100uF capacitor. The final number will probably end in the megaohms range, but the exact number you'll see really depends on the design of your multimeter. My old Fluke 87-III shows about 3.5M.
The power on (but no code enabled VHOST) measurement should show 400 to 600 ohms. The TPD3S014 chip has an active output discharge circuit when power isn't enabled. What's really inside the chip probably isn't a real resistor. It's very likely an analog circuit with mosfets which emulate a resistor, so the exact number you'll read could vary. My Fluke 87-III measures 395 ohms.
TPD3S014 has an overcurrent protection circuit which goes into constant current limit mode. It also has over-temperature protection (but at a very high temperature). That's the reason this chip was chosen for Teensy 3.6 and 4.1, rather than others which go into a fault mode that shuts off the power until some sort of reset is performed. The constant current feature is meant to make the USB host power output "robust" when things go wrong for a brief moment, rather than shutting itself off. If the output is shorted, the chip is supposed to get hot as it tries to keep delivering constant current.
On a good board, the power off measurement should show a gradually increasing number as your multimeter's test current charges the 100uF capacitor. The final number will probably end in the megaohms range, but the exact number you'll see really depends on the design of your multimeter. My old Fluke 87-III shows about 3.5M.
The power on (but no code enabled VHOST) measurement should show 400 to 600 ohms. The TPD3S014 chip has an active output discharge circuit when power isn't enabled. What's really inside the chip probably isn't a real resistor. It's very likely an analog circuit with mosfets which emulate a resistor, so the exact number you'll read could vary. My Fluke 87-III measures 395 ohms.
TPD3S014 has an overcurrent protection circuit which goes into constant current limit mode. It also has over-temperature protection (but at a very high temperature). That's the reason this chip was chosen for Teensy 3.6 and 4.1, rather than others which go into a fault mode that shuts off the power until some sort of reset is performed. The constant current feature is meant to make the USB host power output "robust" when things go wrong for a brief moment, rather than shutting itself off. If the output is shorted, the chip is supposed to get hot as it tries to keep delivering constant current.
PaulStoffregen
Well-known member
Usually measuring such low resistance means the short is metal. Usually when a chip fails, the semiconductor gives a strange reading which depends quite a lot on the test current and range of your multimeter, but rarely does failure inside a chip give such low ohms measurement.