XCORE-200 USB breaks on my custom board
Posted: Fri Feb 10, 2017 7:39 pm
Hi there,
I'm having a problem with my custom XCORE-200 boards. The USB works for a bit, then breaks. I have swapped the XMOS chip out, and again, it works, then breaks.
I'm following the reference design pretty closely, but there is one, perhaps substantial difference in power supply sequencing.
I have the 3.3V bus go high with VBUS, but then the sequencer doesn't power up the 1.0V supply for 15mS. And reset doesn't get released for another 15mS.
So, the power sequence is:
VBUS -> HIGH @ T=0
3.3V -> HIGH @ T=1mS or less.
1.0V -> HIGH @ T=15mS. The actual ramp time is quick -- < 1mS
POW -> RELEASED @ T=30mS
Could this be the source of my problems?
The spec says 1.0V must ramp to high within 10mS, but where is that measured from? 10mS of monotonic ramp from 0V -> 1.0V, which is what I assumed. If it's 10mS from when 3.3V is high, then that could be a problem.
Strangely, this board worked for a good long while with no issues, but then broke and never got better.
The only thing I can think of is that I may have used a laptop when everyting worked, then moved to my desktop which broke things.
Thanks,
-Caleb
I'm having a problem with my custom XCORE-200 boards. The USB works for a bit, then breaks. I have swapped the XMOS chip out, and again, it works, then breaks.
I'm following the reference design pretty closely, but there is one, perhaps substantial difference in power supply sequencing.
I have the 3.3V bus go high with VBUS, but then the sequencer doesn't power up the 1.0V supply for 15mS. And reset doesn't get released for another 15mS.
So, the power sequence is:
VBUS -> HIGH @ T=0
3.3V -> HIGH @ T=1mS or less.
1.0V -> HIGH @ T=15mS. The actual ramp time is quick -- < 1mS
POW -> RELEASED @ T=30mS
Could this be the source of my problems?
The spec says 1.0V must ramp to high within 10mS, but where is that measured from? 10mS of monotonic ramp from 0V -> 1.0V, which is what I assumed. If it's 10mS from when 3.3V is high, then that could be a problem.
Strangely, this board worked for a good long while with no issues, but then broke and never got better.
The only thing I can think of is that I may have used a laptop when everyting worked, then moved to my desktop which broke things.
Thanks,
-Caleb