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SSM3302

Question asked by koebi on Feb 3, 2014
Latest reply on Feb 4, 2014 by koebi

I designed a PCB board with 4 layers with the chip SSM3302. It is mount on the top of the PCB with 9 vias (squared appearance) to all layers. This tiny unit (dimension of approx. 45x28mm) is soldered on a Euro mother board with massive GND plane.
There are two capacitors (470uF each) connected very close to the supply trace wire. I apply 12VDC..18VDC and both channel wired to 2x speaker (4Ohms each). All electrical parts are as recommended by AnalogDevices (low pass filter coil etc.).

Problem: At undefined output power, both (sometimes one of both) channels switch shortly silent with a VERY SHARP and LOUD noise crack. It is observed, that this effect occurs more at low chip temperatures around 20 degrees and a bit less at higher chip temperatures (50 degrees celsius).

 

It looks as the chip does mute very uncoordinated at middle power gain, not at full power. I wired + INL (INL to GND) and + (INR INR to GND). For Information: Both shut down pins (lef+right) are wired to a controller chip and this option work perfectly with NO hump or click effect!

 

Previously, with only two PCB layers, I had the nearly same problem encountered. I guess that the layout has been routed very trust worthy (2 sep GND in the inner layer, supply etc. as shown on the eval. board).

 

I ask for advice.

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