[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.

https://shedsynth.files.wordpress.com/2021/05/adsr-a-schematic-gate-to-d2.pn
g

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,

Al

 

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

 

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