So I have an implementation where the circuit that provides 3.3v to the Teensy is an off-the-shelf part so I can't make any changes to it. The problem is that the risetime to 3.3v is almost 7 milliseconds and about 20 percent of the time the Teensy won't start (by comparison my bench supply brings it up in about 3 milliseconds and I saw one failure, plugging in USB brings it up in about 68uS and there's never been a failure).
In every instance it will work if I power down and back up quickly. So I don't know whether the problem is in the MK20 or the Mini54. Pressing the prog button has no effect.
So my question is 3-fold:
1) are there any settings that we can change on either/both processors that would turn on built-in brownout detection and thus handle this problem without electrical changes.
2) failing that since I can't get to the reset pin on the Teensy I was thinking of getting a supervisor chip and using it to drive a FET that turned on power to the chip. (this isn't really a question, more an invitation for comments on the wisdom/viability of such a solution)
3) I am working on a custom implementation of the Teensy. It is clear now that I need to add a supervisor to this implementation - Should I have the supervisor hold the reset line on the MK20, the mini54 (which currently is un-routed) or both (not tied together obviously, but a 2-channel supervisor)?
Thank you,
DougM
In every instance it will work if I power down and back up quickly. So I don't know whether the problem is in the MK20 or the Mini54. Pressing the prog button has no effect.
So my question is 3-fold:
1) are there any settings that we can change on either/both processors that would turn on built-in brownout detection and thus handle this problem without electrical changes.
2) failing that since I can't get to the reset pin on the Teensy I was thinking of getting a supervisor chip and using it to drive a FET that turned on power to the chip. (this isn't really a question, more an invitation for comments on the wisdom/viability of such a solution)
3) I am working on a custom implementation of the Teensy. It is clear now that I need to add a supervisor to this implementation - Should I have the supervisor hold the reset line on the MK20, the mini54 (which currently is un-routed) or both (not tied together obviously, but a 2-channel supervisor)?
Thank you,
DougM