[sdiy] CV input op-amp circuit
list at mikebeauchamp.com
Mon Dec 7 21:15:55 CET 2020
On 12/5/20 11:38 PM, Brian Willoughby wrote:
> I'm not quite sure how your *external* protection diodes could cause any problems like this, but it's potentially similar to other problems.
You know, I'm not sure either..
I've attached the relevant part of the schematic. The +3.3V-D is coming
directly from the Teensy 3.2 onboard Voltage Regulator (fed from a +5V
regulator - which is fed from a +15V regulated rail).
TUNE-RAW is expected to be -4.1V -> 0V
OSC2-TUNE is expected to be -10.2V -> 0V
My Teensy fails to start properly about 50% of the time like this. When
I remove both BAT54-S's (or disconnect them from +3.3V-D) things start
> In your "fails 50% of the time" are you able to wait for power to
>completely drain from the supply rails as well as all other parts of
>the circuit? Sometimes a resistive load on supply capacitors can help
>drain them when you want to recover from a user that flips the power
>switch too quickly.
Thank you for mentioning this problem as well Brian! I didn't know it
was a thing.. but while testing my BAT54-S problem I also noticed that
if I powered the unit on at a very specific timing after power-down, the
microcontroller would fail to start 100% of the time. With the scope I
could see it was always when the microcontroller supply voltage (which
has a dedicated 10uF cap on it) would drain to a certain range.
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