Zener diode over voltage protection

[MAO]

What's the proper way to add over voltage protection for a MAX1044 using a 9.1v zener?

Thanks,
Mike

[IvIark]

Cathode to supply, anode to ground

[MAO]

Thanks Mark,

Do I need a current limiting resistor, like 100 ohms, between the supply and zener?

Or anything paralleled with the zener?

[IvIark]

It's a good idea to use a current limiting resistor
http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm

[MAO]

Sound advice as usual!

Impatience along with trying to avoid soldering up daughter board got the best of me.

I wired in the lone zener across the DC jack, pulled the MAX1044 (not considering I was probably removing the load off the zener) fired up the pedal with a 9V adapter. No problem. although the voltage coming off the zener was just below the supply output of 9.4v, (I assume because there was no load at this point since I had removed the MAX1044 from the circuit.)

I then plugged in a 12V adapter and about 2 seconds later the zener started to smoke. Luckily I pulled the plug before any further damage was done. The 1N4739 is now an interesting looking jumper wire :0)

Built the daughter board using 2-180 ohm resisters in parallel between another 1N4739 and the dc jack. No smoke with the 12v adapter, plugged the MAX1044 back in and all is well. Just over 9.1v supplying the MAX1044.  

Lesson learned, use a current limiting resistor ahead of the zener! Luckily it only cost me a 4739 and some time.    

[IvIark]

I've seen them used without a CLR, the Klon being the obvious example although that is a 12V zener and from a required 9V supply is probably never doing anything anyway except maybe a bit of protection against spikes, but there are a few others I've come across doing the layouts.  Unless you're using a pretty hefty zener it's always worth including a CLR to make sure