SPiKe™ protection

Ted205

Member
2008-06-17 8:54 am
Hi guys

Does anyone know if the lm3886 SPiKe™ protection causes a buzzing/fuzzing sound when engaged.

I'm getting this aswell as increased heat from the chip but i'm not sure if its spike protection of a current/grounding issue.

any opinions :)
 
I think with SPIKE it just shuts down. But I have seen many of those chips blown up. Is it getting hot? Yeah, I'd scope out your supply rails and look for oscillation. If you don't have a scope, I'd just add some more capacitors on the rails. Also layout of the circuit will make it oscillate if your output is too close to the input. And, lastly, do you have any DC on the output?
 
Hi guys

Does anyone know if the lm3886 SPiKe™ protection causes a buzzing/fuzzing sound when engaged.

I'm getting this aswell as increased heat from the chip but i'm not sure if its spike protection of a current/grounding issue.

any opinions :)

It could be that your speaker cables have a high element of capacitance causing oscillations, or ringing. This will give some audible buzzing, and cause an increase in heat output from the chip.

A zobel network will protect the chip against this kind of problem, and in my opinion has no audible impact on the sound of the amp. I use values of 10R and 0.1uF in parallel with the load (speaker) in my LM3875 Gainclone.

Regards,

Chris.