"Blown" Teensy 3.6 with external voltage derived from LM3671 3.3V Boost converter...
I've got a custom-circuit board for a project with a Teensy 3.6 at its heart. It's powered from a 3.7V Lipo battery.
Previous iterations of the board fed the 3.7V into the VIN pin, and let the Teensy regulate its own voltage. However, to avoid voltage droop, I redesigned it with an LM3671 3.3v boost converter coming from the battery's 3.7V VCC pin, so as to supply a consistent 3.3V until the battery could no longer supply anything.
Here's my schematic for the boost converter -
- and it connects to the 3.3v VCC pins on the Teensy.
(The Teensy has no connections whatsoever to its VIN - there's an external USB socket connected up to the battery charger, and the D+/D- lines broken out to the Teensy, but there's not a backflow through the Teensy's own USB port, because it's not used at all.)
I saw a brief glimmer of a working circuit, but then the prototype ceased functioning. A continuity tester tells me there's now continuity between VCC and GND (on the Teensy 3.6), and about 100mv pd is seen between VCC and GND. Spinning up another board with no teensy attached and I see 3.3V from the converter with a battery connected.
I'm slightly lost as to what could be causing this the moment a Teensy's attached - my gut feel is an onrush of current - but no prior thread on directly powering VCC led to the outcome I was looking for. One answer might be "the current draw from the rest of the circuit that's on that VCC line is higher than the Teensy would like" (there's a low-power TPA2012 speaker amplifier, for instance) - but I'm now deferring to more experienced EEs.
I've got a custom-circuit board for a project with a Teensy 3.6 at its heart. It's powered from a 3.7V Lipo battery.
Previous iterations of the board fed the 3.7V into the VIN pin, and let the Teensy regulate its own voltage. However, to avoid voltage droop, I redesigned it with an LM3671 3.3v boost converter coming from the battery's 3.7V VCC pin, so as to supply a consistent 3.3V until the battery could no longer supply anything.
Here's my schematic for the boost converter -
- and it connects to the 3.3v VCC pins on the Teensy.
(The Teensy has no connections whatsoever to its VIN - there's an external USB socket connected up to the battery charger, and the D+/D- lines broken out to the Teensy, but there's not a backflow through the Teensy's own USB port, because it's not used at all.)
I saw a brief glimmer of a working circuit, but then the prototype ceased functioning. A continuity tester tells me there's now continuity between VCC and GND (on the Teensy 3.6), and about 100mv pd is seen between VCC and GND. Spinning up another board with no teensy attached and I see 3.3V from the converter with a battery connected.
I'm slightly lost as to what could be causing this the moment a Teensy's attached - my gut feel is an onrush of current - but no prior thread on directly powering VCC led to the outcome I was looking for. One answer might be "the current draw from the rest of the circuit that's on that VCC line is higher than the Teensy would like" (there's a low-power TPA2012 speaker amplifier, for instance) - but I'm now deferring to more experienced EEs.