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SSM2603 sporadic audio corruption

Question asked by Pelle@Xelmo on Dec 3, 2013

We have a problem when using the SSM2603 in playback mode. We use it in I2S slave mode with 48 kHz stereo sound and extract it from the Line Out output. After some startups everything works fine, but after about half of the startups the audio is severely corrupted. The signal looks like it's offset upwards and where the signal gets too high it wraps around to the bottom, so it definitely looks like a digital problem. The I2S signal looks fine. Also, the problem comes and goes when only restarting the SSM2603, without restarting the I2S source.

 

After much trouble shooting I finally found a working solution: Until now I followed the startup sequencing described in the CONTROL REGISTER SEQUENCING section of the datasheet. The needed delay should in our case be 72 ms since the capacitor at VMID is rated at 10µF. But if I do point 4. "enable the DAC output path" BEFORE point 3. (delay and set digital core active), it always works.

 

Since I have to break the sequence described in the datasheet in order to make it work, I would like to understand what's going on here.

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