[sdiy] CV input op-amp circuit

[Jay Schwichtenberg]

Mike,

You might do some research on the Teensy 3.2 (https://forum.pjrc.com/). 
There are some power on issues depending on the power supply, if I 
remember correctly it's slow power up thing. On the uO&C they had to add 
a reset manager to get it to power up all the time. Might look under 
uO&C on Muffs too.

Jay S.

On 12/5/2020 5:29 PM, Mike Beauchamp wrote:
>
> Very interesting that you had some sort of problem with the diodes. 
> I've been unsuccessfully trying to debug a problem I've been having 
> where my Teensy 3.2 fails to power on about 50% of the time (the 
> cystal oscillator doesn't oscillate) and it seems to go away 
> completely when I remove two BAT54S's that are protecting some op-amp 
> outputs that are going into ADC pins.
>
> These inputs aren't open to user-voltages so over-voltage scenarios 
> aren't expected, but the BAT54S's are there to protect the Teensy 3.2 
> in case something goes wrong.
>
> Unless I can figure out WHY this is happening, I'm probably just going 
> to remove the diodes and add current limiting resistors.
>
> My guess is that the voltages spike on start-up and somehow freaks the 
> teensy's crystal out.. I know, very technical :)
>
> I've captured the start-up on my scope though, looking at the ADC 
> inputs and all voltages and I see nothing different from when the 
> Teensy fails or succeeds to power-up.
>
> Mike
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