Zener Diode values

[Danbieranowski]

Hey all,

I'm working on a build with an LT1054 which works as a charge pump to get me from 9v to 18v (as far as I understand). This build calls for a 13v Zener diode, but the largest value I have is 12v. Would using a 12v be acceptable? Or is it possible to link a 12v and a 3v in series to make it 15v? Am I a total goof for even considering that? I have not done any real research on zener diodes, so my understanding of what they do is limited.

For anyone curious, it's Aion's version of an EP-3 - https://aionfx.com/app/files/docs/ares_documentation.pdf

Thanks as always,
Dan

 

[benny_profane]

The charge pump in that circuit is there to double your input voltage (i.e., the VA net in the schematic). The zener is there to dump transient power spikes as over-voltage protection for the charge pump. The Schottky is there for reverse polarity protection.

The circuit is designed to work with either 9V input (for 18V operation) or 12V input (for 24V operation). If you're planning on running the circuit at 9V, the 12V zener is perfectly fine. You'd run into issues if you were to input 12V and use a 12V zener, though. If you were constantly at/above 12V, the diode would constantly shunt voltage to ground and you may run into failures. Zener diodes shouldn't be used as regulators.

So, if you're planning on running the circuit at 9V, the 12V zener would be fine. If you're looking to have the option to run it at 12V, you'd want to consider using a 13V zener.

 

[Danbieranowski]

The charge pump in that circuit is there to double your input voltage (i.e., the VA net in the schematic). The zener is there to dump transient power spikes as over-voltage protection for the charge pump. The Schottky is there for reverse polarity protection.

The circuit is designed to work with either 9V input (for 18V operation) or 12V input (for 24V operation). If you're planning on running the circuit at 9V, the 12V zener is perfectly fine. You'd run into issues if you were to input 12V and use a 12V zener, though. If you were constantly at/above 12V, the diode would constantly shunt voltage to ground and you may run into failures. Zener diodes shouldn't be used as regulators.

So, if you're planning on running the circuit at 9V, the 12V zener would be fine. If you're looking to have the option to run it at 12V, you'd want to consider using a 13V zener.

This is such a well-articulated and educational answer that I’d pay you for it. If you’re ever around Portland, I owe you a pizza.

 

[benny_profane]

This is such a well-articulated and educational answer that I’d pay you for it. If you’re ever around Portland, I owe you a pizza.

No problem! Glad to help! I'll keep that pizza in mind if I'm ever up in the PNW.

 

[finebyfine]

I had no idea how to answer your question and tried to piece it together myself to learn more about zeners and @benny_profane 's answer is mind blowingly easy to understand. I wish I had waited for that reply before doing any digging

 

[Danbieranowski]

I had no idea how to answer your question and tried to piece it together myself to learn more about zeners and @benny_profane 's answer is mind blowingly easy to understand. I wish I had waited for that reply before doing any digging

Thank you for even looking into it. I’m grateful for everyone’s help here and I hope y’all know it.