[sdiy] Will clamping diode work when power is off?

ShedSynth shedsynth at gmail.com
Fri May 28 18:57:33 CEST 2021

I have an Arduino-based module, with a GATE input protected by 1K input
resistor then clamping diodes to 0V & +5V.


I find that with power off to that module any GATE or CV to the input can
pull up the module's +5V through the diode and even power the whole case's
+5V rail.

The clue was seeing the case's +5V LED flashing in time with the GATE input.


And I think that if the input is more than +5V, the un-powered voltage
regulator will not be able to regulate so digital components (and perhaps
the voltage regulator itself) might be damaged.

Have I understood this correctly?


I'm wondering whether to put a 5.1V zener across the module's 0V and +5V to
catch any over-voltage.

Have I understood THAT correctly?


Thanks in advance,



SHEDSYNTH <https://shedsynth.wordpress.com/>  - home-knitted eurorack


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20210528/b5535b0b/attachment.htm>

More information about the Synth-diy mailing list