I'm looking at running an AD1938, using the internal PLL to generate a clock off of the LRCLK. If I do that, what should I do with the MCLKI and MCLKO pins? Terminate them? Leave them float?
It is OK to let both pins float, however if you can spare a component and some board space, I would recommend using a 0R00 ohm resistor to short the MCLKI pin to ground. This will give you the opportunity to connect a clock to that pin if you would like to try other options, and it will keep the input to the MCLKI node quiet if you do not use it. MCLKO should be shut off in the registers, PLL Clock Control 0: 0x00 [4:3] set to b11.
Ah, perfect! I think I can squeeze in another 0603!
Also, off topic, I sent you a screen capture from my scope on the other issue you're helping me with. Please let me know if it doesn't come through.
Thanks for the help!
Here is a protection scheme that should help. Using a BAT54S, you can connect pin 2 cathode to your AVDD rail, pin 3 should be attached to your audio line and pin 1 anode should be connected to ground. If the audio signal goes 0.2 V above rail, the signal will be clamped to the rail, and if it goes 0.2 V below ground, the signal will be clamped to ground. Put this diode on the source side of the AC coupling, if there is any.
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