- Wed Feb 24, 2010 4:53 pm
#94464
I'll add that I am powering my project from a Texas Instruments TPS61070 3.3V boost converter, not from batteries direct or from a wall wart.
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lordsteve wrote:I checked continuity between pins 2 and 5. When no plug was inserted, the resistance was infinite (humor me). When I inserted the plug into the jack, there was a point when pin 2 was shorted to pin 5 -- the resistance dropped to 1 (one) ohm -- then went back to infinity after insertion was complete.That is totally consistent with what esklar81 and JonChandler said earlier. I can get this to happen with my connector as well. When you insert the plug there will be a time when the tip of the plug will short pins 2 and 5 (the tip first touches pin 2. As the plug insertion continues it will also touch pin 5. Finally when the plug is entirely inserted the tip will not be touching pin 2).
lordsteve wrote:The jack was not wired to anything and there was no plug inserted. The resistance I deemed a short was 1 (one) ohm. When I say left is shorted to right, I mean that the left audio signal is shorted to the right audio signal. This happens momentarily when a plug is inserted. When the short occurs...brown out. When I manually short the left audio channel to the right audio channel, same thing...brown out.I'm still failing to understand your hardware. If "the jack was not wired to anything", then how can "the short occurs...brown out"??? What's being shorted or browned out?
lordsteve wrote:I'm assuming this is a common problem and must happen frequently. There has to be some way to handle it.While it's a "common" occurrence, I don't think it's all that common a "problem". In typical audio applications, people tolerate not having good audio in either the speakers or the headset while they're inserting the plug. As long as the signal quality isn't impaired by the short for more than the fraction of a second it takes to insert the plug, I doubt most people notice this or would care about it if they did.
lordsteve wrote:The problem in my project is not audio quality, but rather that when inserting the headphones plug, the shorting of the left and right channel inputs causes a brown out condition.I have a few questions:
lordsteve wrote:One thing I noticed in the MAX4410 datasheet is a sentence about the soldering profile. It says that hand soldering is not allowed. I suppose it is possible that hand soldering, especially my very n00b soldering, could do something to the short circuit protection of the MAX4410.Hand soldering is not "allowed"/recommended for the UCSP version (the package with the bumps). The SSOP version is rated for 10 seconds at 300 degrees C, so you're fine. I doubt your soldering would damage the short circuit protection while the rest of the chip works fine.
lordsteve wrote:Could I add a small surface-mount isolation transformer to each channel to isolate the headphones from the chip? What parameters of the transformers do I need to look for?As the chip is designed to directly drive a 32 ohm load, I have no idea if adding transformers will help or hurt you. I would think the later.